CSL 1.0.2 Specification

Principal Authors Rintze M. Zelle, PhD, Brenton M. Wiernik, Frank G. Bennett, Jr., Bruce D'Arcus, Denis Maier

with additional contributions from Julien Gonzalez, Sebastian Karcher, Sylvester Keil, Cormac Relf, Lars Willighagen, and other CSL contributors.

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Table of Contents

Introduction
- Terminology
Namespacing
Whitespace Handling
File Types
XML Declaration
Styles - Structure
- The Root Element - cs:style
- Child Elements of cs:style
  - Info
  - Citation
  - Bibliography
  - Macro
  - Locale
    - Locale Fallback
Locale Files - Structure
Rendering Elements
- Layout
- Text
- Date
- Number
- Names
- Label
- Group
- Choose
Style Behavior
Appendix I - Categories
Appendix II - Terms
Appendix III - Types
Appendix IV - Variables
Appendix V - Page Range Formats
Appendix VI: Links

Introduction

The Citation Style Language (CSL) is an XML-based format to describe the formatting of citations, notes and bibliographies, offering:

An open format
Compact and robust styles
Extensive support for style requirements
Automatic style localization
Infrastructure for style distribution and updating
Thousands of freely available styles (Creative Commons BY-SA licensed)

For additional documentation, the CSL schema, styles, and locales, visit the CSL project home, citationstyles.org.

Terminology

The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, are to be interpreted as described in IETF RFC 2119.

The CSL XML namespace URI is "http://purl.org/net/xbiblio/csl". The namespace prefix cs: is used throughout this specification when referring to CSL elements, but is generally omitted in favor of a default namespace declaration (set with the xmlns attribute) on the root cs:style or cs:locale element.

Whitespace Handling

CSL styles are valid XML, but CSL processors MUST NOT normalize attribute values by trimming leading or trailing whitespace from attributes which define text that is intended for output:

after-collapse-delimiter
cite-group-delimiter
delimiter
initialize-with
name-delimiter
names-delimiter
prefix
range-delimiter
sort-separator
suffix
year-suffix-delimiter
value

File Types

There are three types of CSL files: independent and dependent styles (both types use the ".csl" extension), and locale files (named "locales-xx-XX.xml", where "xx-XX" is a language dialect, e.g. "en-US" for American English).

Independent Styles

Independent styles contain formatting instructions for citations, notes and bibliographies. While mostly self-contained, they rely on locale files for (default) localization data.

Dependent Styles

A dependent style is an alias for an independent style. Its contents are limited to style metadata, and doesn't include any formatting instructions (the sole exception is that dependent styles can specify an overriding style locale). By linking dependent styles for journals that share the same citation style (e.g., "Nature Biotechnology", "Nature Nanotechnology", etc.) to a single independent style (e.g., "Nature Journals"), there is no need to duplicate formatting instructions.

Locale Files

Each locale file contains a set of localization data (term translations, localized date formats, and grammar options) for a particular language dialect.

XML Declaration

Each style or locale should begin with an XML declaration, specifying the XML version and character encoding. In most cases, the declaration will be:

<?xml version="1.0" encoding="UTF-8"?>

Styles - Structure

The Root Element - `cs:style`

The root element of styles is cs:style. In independent styles, the element carries the following attributes:

class: Determines whether the style uses in-text citations (value "in-text") or notes ("note").
default-locale (optional): Sets a default locale for style localization. Value must be a locale code.
version: The CSL version of the style. Must be "1.0" for CSL 1.0-compatible styles.

In addition, cs:style may carry any of the global options and inheritable name options.

Of these attributes, only version is required on cs:style in dependent styles, while the default-locale attribute may be set to specify an overriding style locale. The other attributes are allowed but ignored.

An example of cs:style for an independent style, preceded by the XML declaration:

<?xml version="1.0" encoding="UTF-8"?>
<style xmlns="http://purl.org/net/xbiblio/csl" version="1.0" class="in-text" default-locale="fr-FR"/>

Child Elements of `cs:style`

In independent styles, the cs:style root element has the following child elements:

cs:info: Must appear as the first child element of cs:style. Contains the metadata describing the style (style name, ID, authors, etc.).
cs:citation: Must appear once. Describes the formatting of in-text citations or notes.
cs:bibliography (optional): May appear once. Describes the formatting of the bibliography.
cs:macro (optional): May appear multiple times. Macros allow formatting instructions to be reused, keeping styles compact and maintainable.
cs:locale (optional): May appear multiple times. Used to specify (overriding) localization data.

In dependent styles, cs:style has only one child element, cs:info.

Info

The cs:info element contains the style's metadata. Its structure is based on the Atom Syndication Format.

In independent styles, cs:info has the following child elements:

cs:author and cs:contributor (optional)

cs:author and cs:contributor, used to respectively acknowledge style authors and contributors, may each be used multiple times. Within these elements, the child element cs:name must appear once, while cs:email and cs:uri each may appear once. These child elements should contain respectively the name, email address and URI of the author or contributor.

cs:category (optional)

Styles may be assigned one or more categories. cs:category may be used once to describe how in-text citations are rendered, using the citation-format attribute set to one of the following values:

"author-date" - e.g. "… (Doe, 1999)"
"author" - e.g. "… (Doe)"
"numeric" - e.g. "… [1]"
"label" - e.g. "… [doe99]"
"note" - the citation appears as a footnote or endnote

cs:category may be used multiple times with the field attribute, set to one of the discipline categories (see Appendix I - Categories), to indicates the field(s) for which the style is relevant.

cs:id

Must appear once and contain a stable, unique identifier to establish the identity of the style. For historical reasons, existing styles may use URIs, but new styles should use a UUID to guarantee stability and uniqueness.

cs:issn/cs:eissn/cs:issnl (optional)

The cs:issn element may be used multiple times to indicate the ISSN identifier(s) of the journal for which the style was written. The cs:eissn and cs:issnl elements may each be used once for the eISSN and ISSN-L identifiers, respectively.

cs:link (optional)

May be used multiple times. cs:link must carry two attributes: href, set to a URI (usually a URL), and rel, whose value indicates how the URI relates to the style. The possible values of rel:

"self" - style URI
"template" - URI of the style from which the current style is derived
"documentation" - URI of style documentation

The cs:link element may contain content describing the link.

cs:published (optional)

May appear once. The contents of cs:published must be a timestamp, indicating when the style was initially created or made available.

cs:rights (optional)

May appear once. The contents of cs:rights specifies the license under which the style file is released. The element may carry a license attribute to specify the URI of the license.

cs:summary (optional)

May appear once. The contents of cs:summary gives a (short) description of the style.

cs:title

Must appear once. The contents of cs:title should be the name of the style as shown to users.

cs:title-short (optional)

May appear once. The contents of cs:title-short should be a shortened style name (e.g. "APA").

cs:updated

Must appear once. The contents of cs:updated must be a timestamp that shows when the style was last updated.

The cs:link, cs:rights, cs:summary, cs:title and cs:title-short elements may carry a xml:lang attribute to specify the language of the element's content (the value must be an xsd:language locale code). For cs:link, the attribute can also be used to indicate the language of the link target.

In dependent styles, cs:link must be used with rel set to "independent-parent", with the URI of the independent parent style set on href. In addition, cs:link may not be used with rel set to "template".

An example of cs:info for an independent style:

<info>
  <title>Style Title</title>
  <id>http://www.zotero.org/styles/style-title</id>
  <link href="http://www.zotero.org/styles/style-title" rel="self"/>
  <link href="http://www.example.org/instructions-to-authors#references" rel="documentation"/>
  <author>
    <name>Author Name</name>
    <email>name@example.org</email>
    <uri>http://www.example.org/name</uri>
  </author>
  <category citation-format="author-date"/>
  <category field="zoology"/>
  <updated>2011-10-29T21:01:24+00:00</updated>
  <rights license="http://creativecommons.org/licenses/by-sa/3.0/">This work
  is licensed under a Creative Commons Attribution-ShareAlike 3.0 License</rights>
</info>

Citation

The cs:citation element describes the formatting of citations, which consist of one or more references ("cites") to bibliographic sources. Citations appear in the form of either in-text citations (in the author (e.g. "[Doe]"), author-date ("[Doe 1999]"), label ("[doe99]") or number ("[1]") format) or notes. The required cs:layout child element describes what, and how, bibliographic data should be included in the citations (see Layout). cs:layout may be preceded by a cs:sort element, which can be used to specify how cites within a citation should be sorted (see Sorting). The cs:citation element may carry attributes for Citation-specific Options and Inheritable Name Options. An example of a cs:citation element:

<citation>
  <sort>
    <key variable="citation-number"/>
  </sort>
  <layout>
    <text variable="citation-number"/>
  </layout>
</citation>

A note to CSL processor developers In note styles, a citation is often a sentence by itself. Therefore, the first character of a citation should preferably be uppercased when there is no preceding text in the note. In all other cases (e.g. when a citation is inserted into the middle of a pre-existing footnote), the citation should be printed as is.

Bibliography

The cs:bibliography element describes the formatting of bibliographies, which list one or more bibliographic sources. The required cs:layout child element describes how each bibliographic entry should be formatted. cs:layout may be preceded by a cs:sort element, which can be used to specify how references within the bibliography should be sorted (see Sorting). The cs:bibliography element may carry attributes for Bibliography-specific Options and Inheritable Name Options. An example of a cs:bibliography element:

<bibliography>
  <sort>
    <key macro="author"/>
  </sort>
  <layout>
    <group delimiter=". ">
      <text macro="author"/>
      <text variable="title"/>
    </group>
  </layout>
</bibliography>

Macro

Macros, defined with cs:macro elements, contain formatting instructions. Macros can be called with cs:text from within other macros and the cs:layout element of cs:citation and cs:bibliography, and with cs:key from within cs:sort of cs:citation and cs:bibliography. It is recommended to place macros after any cs:locale elements and before the cs:citation element.

Macros are referenced by the value of the required name attribute on cs:macro. The cs:macro element must contain one or more rendering elements.

The use of macros can improve style readability, compactness and maintainability. It is recommended to keep the contents of cs:citation and cs:bibliography compact and agnostic of item types (e.g. books, journal articles, etc.) by depending on macro calls. To allow for easy reuse of macros in other styles, it is recommended to use common macro names.

In the example below, cites consist of the item title, rendered in italics when the item type is "book":

<style>
  <macro name="title">
    <choose>
      <if type="book">
        <text variable="title" font-style="italic"/>
      </if>
      <else>
        <text variable="title"/>
      </else>
    </choose>
  </macro>
  <citation>
    <layout>
      <text macro="title"/>
    </layout>
  </citation>
</style>

Delimiters from any ancestor delimiting element are not applied within the output of a <text macro="..."> element (see delimiter).

Locale

Localization data, by default drawn from the "locales-xx-XX.xml" locale files, may be redefined or supplemented with cs:locale elements, which should be placed directly after the cs:info element.

The value of the optional xml:lang attribute on cs:locale, which must be set to an xsd:language locale code, determines which languages or language dialects are affected (see Locale Fallback).

See Terms, Localized Date Formats and Localized Options for further details on the use of cs:locale.

An example of cs:locale in a style:

<style>
  <locale xml:lang="en">
    <terms>
      <term name="editortranslator" form="short">
        <single>ed. &amp; trans.</single>
        <multiple>eds. &amp; trans.</multiple>
      </term>
    </terms>
  </locale>
</style>

Locale Fallback

Locale files provide localization data for language dialects (e.g. "en-US" for American English), whereas the optional cs:locale elements in styles can either lack the xml:lang attribute, or have it set to either a language (e.g. "en" for English) or dialect. Locale fallback is the mechanism determining from which of these sources each localizable unit (a date format, localized option, or specific form of a term) is retrieved.

For dialects of the same language, one is designated the primary dialect. All others are secondaries. At the moment of writing, the available locale files include:

Primary dialect	Secondary dialect(s)
de-DE (German)	de-AT (Austria), de-CH (Switzerland)
en-US (English)	en-GB (UK)
es-ES (Spanish)	es-CL (Chile), es-MX (Mexico)
fr-FR (French)	fr-CA (Canada)
pt-PT (Portuguese)	pt-BR (Brazil)
zh-CN (Chinese)	zh-TW (Taiwan)

Locale fallback is best described with an example. If the chosen output locale is "de-AT" (Austrian German), localizable units are individually drawn from the following sources, in decreasing order of priority:

In-style cs:locale elements
1. xml:lang set to chosen dialect, "de-AT"
2. xml:lang set to matching language, "de" (German)
3. xml:lang not set
Locale files
1. xml:lang set to chosen dialect, "de-AT"
2. xml:lang set to matching primary dialect, "de-DE" (Standard German) (only applicable when the chosen locale is a secondary dialect)
3. xml:lang set to "en-US" (American English)

If the chosen output locale is a language (e.g. "de"), the (primary) dialect is used in step 1 (e.g. "de-DE").

Fallback stops once a localizable unit has been found. For terms, this even is the case when they are defined as empty strings (e.g. <term name="and"/> or <term name="and"></term>). Locale fallback takes precedence over fallback of term forms (see Terms).

Locale Files - Structure

While localization data can be included in styles (see Locale), locale files conveniently provide sets of default localization data, consisting of terms, date formats and grammar options.

Each locale file contains localization data for a single language dialect. This locale code is set on the required xml:lang attribute on the cs:locale root element. The same locale code must also be used in the file name of the locale file (the "xx-XX" in "locales-xx-XX.xml"). The root element must carry the version attribute, indicating the CSL version of the locale file (must be "1.0" for CSL 1.0-compatible locale files). Locale files have the same requirements for namespacing as styles. The cs:locale element may contain cs:info as its first child element, and requires the child elements cs:terms, cs:date and cs:style-options (these elements are described below). An example showing part of a locale file:

<?xml version="1.0" encoding="UTF-8"?>
<locale xml:lang="en-US" version="1.0" xmlns="http://purl.org/net/xbiblio/csl">
  <style-options punctuation-in-quote="true"/>
  <date form="text">
    <date-part name="month" suffix=" "/>
    <date-part name="day" suffix=", "/>
    <date-part name="year"/>
  </date>
  <date form="numeric">
    <date-part name="year"/>
    <date-part name="month" form="numeric" prefix="-" range-delimiter="/"/>
    <date-part name="day" prefix="-" range-delimiter="/"/>
  </date>
  <terms>
    <term name="no date">n.d.</term>
    <term name="et-al">et al.</term>
    <term name="page">
      <single>page</single>
      <multiple>pages</multiple>
    </term>
    <term name="page" form="short">
      <single>p.</single>
      <multiple>pp.</multiple>
    </term>
  </terms>
</locale>

Info

The cs:info element may be used to give metadata on the locale file. It has the following child elements:

cs:translator (optional): cs:translator, used to acknowledge locale translators, may be used multiple times. Within the element, the child element cs:name must appear once, while cs:email and cs:uri each may appear once. These child elements should contain respectively the name, email address and URI of the translator.
cs:rights (optional): May appear once. The contents of cs:rights specifies the license under which the locale file is released. The element may carry a license attribute to specify the URI of the license, and a xml:lang attribute to specify the language of the element's content (the value must be an xsd:language locale code).
cs:updated (optional): May appear once. The contents of cs:updated must be a timestamp that shows when the locale file was last updated.

Terms

Terms are localized strings (e.g. by using the "and" term, "Doe and Smith" automatically becomes "Doe und Smith" when the style locale is switched from English to German). Terms are defined with cs:term elements, child elements of cs:terms. Each cs:term element must carry a name attribute, set to one of the terms listed in Appendix II - Terms.

Terms are either directly defined in the content of cs:term, or, in cases where singular and plural variants are needed (e.g. "page" and "pages"), in the content of the child elements cs:single and cs:multiple, respectively.

Terms may be defined for specific forms by using cs:term with the optional form attribute set to:

"long" - (default), e.g. "editor" and "editors" for the "editor" term
"short" - e.g. "ed." and "eds." for the term "editor"
"verb" - e.g. "edited by" for the term "editor"
"verb-short" - e.g. "ed." for the term "editor"
"symbol" - e.g. "§" and "§§" for the term "section"

If a style uses a term in a form that is undefined (even after Locale Fallback), there is fallback to other forms: "verb-short" first falls back to "verb", "symbol" first falls back to "short", and "verb" and "short" both fall back to "long". In addition, the terms "long-ordinal-01" to "long-ordinal-10" fall back to the set of ordinal suffix terms. If no locale or form fallback is available, the term is rendered as an empty string.

The match, gender, and gender-form attributes can be used on cs:term for the formatting of number variables rendered as ordinals (e.g. "first", "2nd"). See Ordinal Suffixes and Gender-specific Ordinals below.

Term content should not contain markup such as LaTeX or HTML. Superscripted Unicode characters can be used for superscripting.

Ordinal Suffixes

Number variables can be rendered with cs:number in the "ordinal" form, e.g. "2nd" (see Number). The ordinal suffixes ("nd" for "2nd") are defined with terms.

The "ordinal" term defines the default ordinal suffix. This default suffix may be overridden for certain numbers with the following terms:

"ordinal-00" through "ordinal-09" - by default, a term in this group is used when the last digit in the term name matches the last digit of the rendered number. E.g. "ordinal-00" would match the numbers "0", "10", "20", etc. By setting the optional match attribute to "last-two-digits" ("last-digit" is the default), matches are limited to numbers where the two last digits agree ("0", "100", "200", etc.). When match is set to "whole-number", there is only a match if the number is the same as that of the term.
"ordinal-10" through "ordinal-99" - by default, a term in this group is used when the last two digits in the term name match the last two digits of the rendered number. When the optional match attribute is set to "whole-number" ("last-two-digits" is the default), there is only a match if the number is the same as that of the term.

When a number has matching terms from both groups (e.g. "13" can match "ordinal-03" and "ordinal-13"), the term from the "ordinal-10" through "ordinal-99" group is used.

Ordinal terms work differently in CSL 1.0.1 and later than they did in CSL 1.0. When neither the style or locale file define the "ordinal" term, but do define the terms "ordinal-01" through "ordinal-04", the original CSL 1.0 scheme is used: "ordinal-01" is used for numbers ending on a 1 (except those ending on 11), "ordinal-02" for those ending on a 2 (except those ending on 12), "ordinal-03" for those ending on a 3 (except those ending on 13) and "ordinal-04" for all other numbers.

The "ordinal" term, and "ordinal-00" through "ordinal-99" terms, behave differently from other terms when it comes to Locale Fallback. Whereas other terms can be (re)defined individually, (re)defining any of the ordinal terms through cs:locale replaces all previously defined ordinal terms.

Long Ordinals

Number variables can be rendered with cs:number in the "long-ordinal" form, e.g. "second" (see Number). The long ordinal terms (e.g. "second" for "2") are defined with the "long-ordinal-01" through "long-ordinal-10" terms.

Long ordinal forms are available for the numbers 1 through 10. For other numbers "long-ordinal" falls back to "ordinal".

For the numbers 1 through 10 in "long-ordinal" form, the match attribute is always treated as "whole-number". For other numbers rendered in "long-ordinal" form, the optional match attribute follows the behavior described in Ordinal Suffixes ("last-two-digits" is the default).

Gender-specific Ordinals

Some languages use gender-specific ordinals. For example, the English "1st" and "first" translate in French to "1^er" and "premier" if the target noun is masculine, and "1^re" and "première" if the noun is feminine.

Feminine and masculine variants of the ordinal terms (see Ordinals) may be specified by setting the gender-form attribute to "feminine" or "masculine" (the term without gender-form represents the neuter variant). There are two types of target nouns: a) the terms accompanying the number variables, and b) the month terms (see Months). The gender of these nouns may be specified on the "long" (default) form of the term using the gender attribute (set to "feminine" or "masculine"). When a number variable is rendered with cs:number in the "ordinal" or "long-ordinal" form, the ordinal term of the same gender is used, with a fallback to the neuter variant if the feminine or masculine variant is undefined. When the "day" date-part is rendered in the "ordinal" form, the ordinal gender is matched against that of the month term.

The example below gives "1re éd." ("1st ed."), "1er janvier" ("January 1st"), and "3e édition" ("3rd edition"):

<?xml version="1.0" encoding="UTF-8"?>
<locale xml:lang="fr-FR">
  <terms>
    <term name="edition" gender="feminine">
      <single>édition</single>
      <multiple>éditions</multiple>
    </term>
    <term name="edition" form="short">éd.</term>
    <term name="month-01" gender="masculine">janvier</term>
    <term name="ordinal">e</term>
    <term name="ordinal-01" gender-form="feminine" match="whole-number">re</term>
    <term name="ordinal-01" gender-form="masculine" match="whole-number">er</term>
  </terms>
</locale>

Localized Date Formats

Two localized date formats can be defined with cs:date elements: a "numeric" (e.g. "12-15-2005") and a "text" format (e.g. "December 15, 2005"). The format is set on cs:date with the required form attribute.

A date format is constructed using cs:date-part child elements (see Date-part). With a required name attribute set to either day, month or year, the order of these elements reflects the display order of respectively the day, month, and year. The date can be formatted with formatting and text-case attributes on the cs:date and cs:date-part elements. The delimiter attribute may be set on cs:date to specify the delimiter for the cs:date-part elements, and affixes may be applied to the cs:date-part elements.

Note Affixes are not allowed on cs:date when defining localized date formats. This restriction is in place to separate locale-specific affixes (set on the cs:date-part elements) from any style-specific affixes (set on the calling cs:date element), such as parentheses. An example of a macro calling a localized date format:

<macro name="issued">
 <date variable="issued" form="numeric" prefix="(" suffix=")"/>
</macro>

Localized Options

There are two localized options, limit-day-ordinals-to-day-1 and punctuation-in-quote (see Locale Options). These global options (which affect both citations and the bibliography) are set as optional attributes on cs:style-options.

Rendering Elements

Rendering elements specify which, and in what order, pieces of bibliographic metadata are included in citations and bibliographies, and offer control over their formatting.

Layout

The cs:layout rendering element is a required child element of cs:citation and cs:bibliography. It must contain one or more of the other rendering elements described below, and may carry affixes and formatting attributes. When used within cs:citation, the delimiter attribute may be used to specify a delimiter for cites within a citation. For example, a citation like "(1, 2)" can be achieved with:

<citation>
  <layout prefix="(" suffix=")" delimiter=", ">
    <text variable="citation-number"/>
  </layout>
</citation>

Text

The cs:text rendering element outputs text. It must carry one of the following attributes to select what should be rendered:

variable - renders the text contents of a variable. Attribute value must be one of the standard variables. May be accompanied by the form attribute to select the "long" (default) or "short" form of a variable (e.g. the full or short title). If the "short" form is selected but unavailable, the "long" form is rendered instead.
macro - renders the text output of a macro. Attribute value must match the value of the name attribute of a cs:macro element (see Macro).
term - renders a term. Attribute value must be one of the terms listed in Appendix II - Terms. May be accompanied by the plural attribute to select the singular ("false", default) or plural ("true") variant of a term, and by the form attribute to select the "long" (default), "short", "verb", "verb-short" or "symbol" form variant (see also Terms).
value - renders the attribute value itself.

An example of cs:text rendering the "title" variable:

<text variable="title"/>

cs:text may also carry affixes, display, formatting, quotes, strip-periods and text-case attributes.

Date

The cs:date rendering element outputs the date selected from the list of date variables with the required variable attribute. A date can be rendered in either a localized or non-localized format.

Localized date formats are selected with the optional form attribute, which must be set to either "numeric" (for fully numeric formats, e.g. "12-15-2005"), or "text" (for formats with a non-numeric month, e.g. "December 15, 2005"). Localized date formats can be customized in two ways. First, the date-parts attribute may be used to show fewer date parts. The possible values are:

"year-month-day" - (default), renders the year, month and day
"year-month" - renders the year and month
"year" - renders the year

Secondly, cs:date may have one or more cs:date-part child elements (see Date-part). The attributes set on these elements override those specified for the localized date formats (e.g. to get abbreviated months for all locales, the form attribute on the month-cs:date-part element can be set to "short"). These cs:date-part elements do not affect which, or in what order, date parts are rendered. Affixes, which are very locale-specific, are not allowed on these cs:date-part elements.

In the absence of the form attribute, cs:date describes a self-contained non-localized date format. In this case, the date format is constructed using cs:date-part child elements. With a required name attribute set to either day, month or year, the order of these elements reflects the display order of respectively the day, month, and year. The date can be formatted with formatting attributes on the cs:date-part elements, as well as several cs:date-part-specific attributes (see Date-part). The delimiter attribute may be set on cs:date to specify the delimiter for the cs:date-part elements, and affixes may be applied to the cs:date-part elements.

For both localized and non-localized dates, cs:date may carry affixes, display, formatting and text-case attributes.

Date-part

The cs:date-part elements control how date parts are rendered. Unless the parent cs:date element calls a localized date format, they also determine which, and in what order, date parts appear. A cs:date-part element describes the date part selected with the required name attribute:

"day"

For "day", cs:date-part may carry the form attribute, with values:

"numeric" - (default), e.g. "1"
"numeric-leading-zeros" - e.g. "01"
"ordinal" - e.g. "1st"

Some languages, such as French, only use the "ordinal" form for the first day of the month ("1er janvier", "2 janvier", "3 janvier", etc.). Such output can be achieved with the "ordinal" form and use of the limit-day-ordinals-to-day-1 attribute (see Locale Options).

"month"

For "month", cs:date-part may carry the strip-periods and form attributes. In locale files, month abbreviations (the "short" form of the month terms) should be defined with periods if applicable (e.g. "Jan.", "Feb.", etc.). These periods can be removed by setting strip-periods to "true" ("false" is the default). The form attribute can be set to:

"long" - (default), e.g. "January"
"short" - e.g. "Jan."
"numeric" - e.g. "1"
"numeric-leading-zeros" - e.g. "01"

"year"

For "year", cs:date-part may carry the form attribute, with values:

"long" - (default), e.g. "2005"
"short" - e.g. "05"

cs:date-part may also carry formatting, text-case and range-delimiter (see Date Ranges) attributes. Attributes for affixes are allowed, unless cs:date calls a localized date format.

Date Ranges

The default delimiter for dates in a date range is an en-dash (e.g. "May–July 2008"). Custom range delimiters can be set on cs:date-part elements with the optional range-delimiter attribute. When a date range is rendered, the range delimiter is drawn from the cs:date-part element matching the largest date part ("year", "month", or "day") that differs between the two dates. For example,

<style>
  <citation>
    <layout>
      <date variable="issued">
        <date-part name="day" suffix=" " range-delimiter="-"/>
        <date-part name="month" suffix=" "/>
        <date-part name="year" range-delimiter="/"/>
      </date>
    </layout>
  </citation>
</style>

would result in "1-4 May 2008", "May–July 2008" and "May 2008/June 2009".

AD and BC

The "ad" term (Anno Domini) is automatically appended to positive years of less than four digits (e.g. "79" becomes "79AD"). The "bc" term (Before Christ) is automatically appended to negative years (e.g. "-2500" becomes "2500BC").

Seasons

If a date includes a season instead of a month, a season term ("season-01" to "season-04", respectively Spring, Summer, Autumn and Winter) take the place of the month term. E.g.,

<style>
  <citation>
    <layout>
      <date variable="issued">
        <date-part name="month" suffix=" "/>
        <date-part name="year"/>
      </date>
    </layout>
  </citation>
</style>

would result in "May 2008" and "Winter 2009".

Approximate Dates

Approximate dates test "true" for the is-uncertain-date conditional (see Choose). For example,

<style>
  <citation>
    <layout>
      <choose>
        <if is-uncertain-date="issued">
          <text term="circa" form="short" suffix=" "/>
        </if>
      </choose>
      <date variable="issued">
        <date-part name="year"/>
      </date>
    </layout>
  </citation>
</style>

would result in "2005" (normal date) and "ca. 2003" (approximate date).

Number

The cs:number rendering element outputs the number variable selected with the required variable attribute. Number variables are a subset of the list of standard variables.

If a number variable is rendered with cs:number and only contains numeric content (as determined by the rules for is-numeric, see Choose), the number(s) are extracted. Variable content is rendered "as is" when the variable contains any non-numeric content (e.g. "Special edition").

During the extraction, numbers separated by a hyphen are stripped of intervening spaces ("2 - 4" becomes "2-4"). Numbers separated by a comma receive one space after the comma ("2,3" and "2 , 3" become "2, 3"), while numbers separated by an ampersand receive one space before and one after the ampersand ("2&3" becomes "2 & 3").

Extracted numbers can be formatted via the optional form attribute, with values:

"numeric" - (default), e.g. "1", "2", "3"
"ordinal" - e.g. "1st", "2nd", "3rd". Ordinal suffixes are defined with terms (see Ordinal Suffixes).
"long-ordinal" - e.g. "first", "second", "third". Long ordinals are defined with the terms "long-ordinal-01" to "long-ordinal-10", which are used for the numbers 1 through 10. For other numbers "long-ordinal" falls back to "ordinal".
"roman" - e.g. "i", "ii", "iii"

Numbers with prefixes or suffixes are never ordinalized or rendered in roman numerals (e.g. "2E" remains "2E). Numbers without affixes are individually transformed ("2, 3" can become "2nd, 3rd", "second, third" or "ii, iii").

cs:number may carry affixes, display, formatting and text-case attributes.

Names

The cs:names rendering element outputs the contents of one or more name variables (selected with the required variable attribute), each of which can contain multiple names (e.g. the "author" variable contains all the author names of the cited item). If multiple variables are selected (separated by single spaces, see example below), each variable is independently rendered in the order specified, with one exception: when the selection consists of "editor" and "translator", and when the contents of these two name variables is identical, then the contents of only one name variable is rendered. In addition, the "editortranslator" term is used if the cs:names element contains a cs:label element, replacing the default "editor" and "translator" terms (e.g. resulting in "Doe (editor & translator)"). The delimiter attribute may be set on cs:names to separate the names of the different name variables (e.g. the semicolon in "Doe, Smith (editors); Johnson (translator)").

<names variable="editor translator" delimiter="; ">
  <label prefix=" (" suffix=")"/>
</names>

cs:names has four child elements (discussed below): cs:name, cs:et-al, cs:substitute and cs:label. The cs:names element may carry affixes, display and formatting attributes.

Name

The cs:name element, an optional child element of cs:names, can be used to describe the formatting of individual names, and the separation of names within a name variable. cs:name may carry the following attributes:

and

Specifies the delimiter between the second to last and last name of the names in a name variable. Allowed values are "text" (selects the "and" term, e.g. "Doe, Johnson and Smith") and "symbol" (selects the ampersand, e.g. "Doe, Johnson & Smith").

delimiter

Specifies the text string used to separate names in a name variable. Default is ", " (e.g. "Doe, Smith").

delimiter-precedes-et-al

Determines when the name delimiter or a space is used between a truncated name list and the "et-al" (or "and others") term in case of et-al abbreviation. Allowed values:

"contextual" - (default), name delimiter is only used for name lists truncated to two or more names
- 1 name: "J. Doe et al."
- 2 names: "J. Doe, S. Smith, et al."
"after-inverted-name" - name delimiter is only used if the preceding name is inverted as a result of the name-as-sort-order attribute. E.g. with name-as-sort-order set to "first":
- "Doe, J., et al."
- "Doe, J., S. Smith et al."
"always" - name delimiter is always used
- 1 name: "J. Doe, et al."
- 2 names: "J. Doe, S. Smith, et al."
"never" - name delimiter is never used
- 1 name: "J. Doe et al."
- 2 names: "J. Doe, S. Smith et al."

delimiter-precedes-last

Determines when the name delimiter is used to separate the second to last and the last name in name lists (if and is not set, the name delimiter is always used, regardless of the value of delimiter-precedes-last). Allowed values:

"contextual" - (default), name delimiter is only used for name lists with three or more names
- 2 names: "J. Doe and T. Williams"
- 3 names: "J. Doe, S. Smith, and T. Williams"
"after-inverted-name" - name delimiter is only used if the preceding name is inverted as a result of the name-as-sort-order attribute. E.g. with name-as-sort-order set to "first":
- "Doe, J., and T. Williams"
- "Doe, J., S. Smith and T. Williams"
"always" - name delimiter is always used
- 2 names: "J. Doe, and T. Williams"
- 3 names: "J. Doe, S. Smith, and T. Williams"
"never" - name delimiter is never used
- 2 names: "J. Doe and T. Williams"
- 3 names: "J. Doe, S. Smith and T. Williams"

et-al-min / et-al-use-first

Use of these two attributes enables et-al abbreviation. If the number of names in a name variable matches or exceeds the number set on et-al-min, the rendered name list is truncated after reaching the number of names set on et-al-use-first. The "et-al" (or "and others") term is appended to truncated name lists (see also Et-al). By default, when a name list is truncated to a single name, the name and the "et-al" (or "and others") term are separated by a space (e.g. "Doe et al."). When a name list is truncated to two or more names, the name delimiter is used (e.g. "Doe, Smith, et al."). This behavior can be changed with the delimiter-precedes-et-al attribute.

et-al-subsequent-min / et-al-subsequent-use-first

If used, the values of these attributes replace those of respectively et-al-min and et-al-use-first for subsequent cites (cites referencing earlier cited items).

et-al-use-last

When set to "true" (the default is "false"), name lists truncated by et-al abbreviation are followed by the name delimiter, the ellipsis character, and the last name of the original name list. This is only possible when the original name list has at least two more names than the truncated name list (for this the value of et-al-use-first/et-al-subsequent-min must be at least 2 less than the value of et-al-min/et-al-subsequent-use-first). An example:

A. Goffeau, B. G. Barrell, H. Bussey, R. W. Davis, B. Dujon, H.
Feldmann, … S. G. Oliver

The remaining attributes, discussed below, only affect personal names. Personal names require a "family" name-part, and may also contain "given", "suffix", "non-dropping-particle" and "dropping-particle" name-parts. These name-parts are defined as:

"family" - surname minus any particles and suffixes
"given" - given names, either full ("John Edward") or initialized ("J. E.")
"suffix" - name suffix, e.g. "Jr." in "John Smith Jr." and "III" in "Bill Gates III"
"non-dropping-particle" - name particles that are not dropped when only the surname is shown ("van" in the Dutch surname "van Gogh") but which may be treated separately from the family name, e.g. for sorting
"dropping-particle" - name particles that are dropped when only the surname is shown ("van" in "Ludwig van Beethoven", which becomes "Beethoven", or "von" in "Alexander von Humboldt", which becomes "Humboldt")

The attributes affecting personal names:

form

Specifies whether all the name-parts of personal names should be displayed (value "long", the default), or only the family name and the non-dropping-particle (value "short"). A third value, "count", returns the total number of names that would otherwise be rendered by the use of the cs:names element (taking into account the effects of et-al abbreviation and editor/translator collapsing), which allows for advanced sorting.

initialize

When set to "false" (the default is "true"), given names are no longer initialized when "initialize-with" is set. However, the value of "initialize-with" is still added after initials present in the full name (e.g. with initialize set to "false", and initialize-with set to ".", "James T Kirk" becomes "James T. Kirk").

initialize-with

When set, given names are converted to initials. The attribute value is added after each initial ("." results in "J. J. Doe"). For compound given names (e.g. "Jean-Luc"), hyphenation of the initials can be controlled with the global initialize-with-hyphen option (see Hyphenation of Initialized Names).

name-as-sort-order

Specifies that names should be displayed with the given name following the family name (e.g. "John Doe" becomes "Doe, John"). The attribute has two possible values:

"first" - attribute only has an effect on the first name of each name variable
"all" - attribute has an effect on all names

Note that even when name-as-sort-order changes the name-part order, the display order is not necessarily the same as the sorting order for names containing particles and suffixes (see Name-part order). Also, name-as-sort-order only affects names written in scripts where the given name typically precedes the family name, such as Latin, Greek, Cyrillic and Arabic. In contrast, names written in Asian scripts are always displayed with the family name preceding the given name.

sort-separator

Sets the delimiter for name-parts that have switched positions as a result of name-as-sort-order. The default value is ", " ("Doe, John"). As is the case for name-as-sort-order, this attribute only affects names in scripts that know "given-name family-name" order.

cs:name may also carry affixes and formatting attributes.

Name-part Order

The order of name-parts depends on the values of the form and name-as-sort-order attributes on cs:name, the value of the demote-non-dropping-particle attribute on cs:style (one of the global options), and the script of the individual name. Note that the display and sorting order of name-parts often differs. An overview of the possible orders:

Display order of names in "given-name family-name" scripts (Latin, etc.)

Conditions:	`form` set to "long"
Order:	given dropping-particle non-dropping-particle family suffix
Example:	[Vincent] [] [van] [Gogh] [III]
Example:	[Alexander] [von] [] [Humboldt] [Jr.]

Conditions:	`form` set to "long", name-as-sort-order active, `demote-non-dropping-particle` set to "never" or "sort-only"
Order:	non-dropping-particle family given dropping-particle suffix
Example:	[van] [Gogh], [Vincent] [], [III]

Conditions:	`form` set to "long", name-as-sort-order active, `demote-non-dropping-particle` set to "display-and-sort"
Order:	family given dropping-particle non-dropping-particle suffix
Example:	[Gogh], [Vincent] [] [van], [III]

Conditions:	`form` set to "short"
Order:	non-dropping-particles family
Example:	[van] [Gogh]

Sorting order of names in "given-name family-name" scripts (Latin, etc.)

N.B. The sort keys are listed in descending order of priority.

Conditions:	`demote-non-dropping-particle` set to "never"
Order:	non-dropping-particle + family dropping-particle given suffix
Example:	[van Gogh] [] [Vincent] [III]

Conditions:	`demote-non-dropping-particle` set to "sort-only" or "display-and-sort"
Order:	family dropping-particle + non-dropping-particle given suffix
Example:	[Gogh] [van] [Vincent] [III]

Display and sorting order of names in "family-name given-name" scripts (Chinese, etc.)

Conditions:	`form` set to "long"
Order:	family given
Example:	毛泽东 [Mao Zedong]

Conditions:	`form` set to "short"
Order:	family
Example:	毛 [Mao]

Non-personal names lack name-parts and are sorted as is, although English articles ("a", "an" and "the") at the start of the name are stripped. For example, "The New York Times" sorts as "New York Times".

Name-part Formatting

The cs:name element may contain one or two cs:name-part child elements for name-part-specific formatting. cs:name-part must carry the name attribute, set to either "given" or "family".

If set to "given", formatting and text-case attributes on cs:name-part affect the "given" and "dropping-particle" name-parts. affixes surround the "given" name-part, enclosing any demoted name particles for inverted names.

If set to "family", formatting and text-case attributes affect the "family" and "non-dropping-particle" name-parts. affixes surround the "family" name-part, enclosing any preceding name particles, as well as the "suffix" name-part for non-inverted names.

The "suffix" name-part is not subject to name-part formatting. The use of cs:name-part elements does not influence which, or in what order, name-parts are rendered. An example, yielding names like "Jane DOE":

<names variable="author">
  <name>
    <name-part name="family" text-case="uppercase"/>
  </name>
</names>

Et-al

Et-al abbreviation, controlled via the et-al-… attributes (see Name), can be further customized with the optional cs:et-al element, which must follow the cs:name element (if present).

The formatting attributes may be used on cs:et-al, for example to italicize the "et-al" term:

<names variable="author">
  <et-al font-style="italic"/>
</names>

The term attribute may also be set, to either "et-al" (the default) or "and others", to use either term:

<names variable="author">
  <et-al term="and others"/>
</names>

Substitute

The optional cs:substitute element, which must be included as the last child element of cs:names, adds substitution in case the name variables specified in the parent cs:names element are empty. The substitutions are specified as child elements of cs:substitute, and must consist of one or more rendering elements (with the exception of cs:layout). A shorthand version of cs:names without child elements, which inherits the attributes values set on the cs:name and cs:et-al child elements of the original cs:names element, may also be used. If cs:substitute contains multiple child elements, the first element to return a non-empty result is used for substitution. Substituted variables are suppressed in the rest of the output to prevent duplication. Substituted variables are considered empty for the purposes of determining whether to suppress an enclosing cs:group. If the variable was rendered earlier in the citation, before the "substitute" element, it is not suppressed. An example, where an empty "author" name variable is substituted by the "editor" name variable, or, when no editors exist, by the "title" macro:

<macro name="author">
  <names variable="author">
    <substitute>
      <names variable="editor"/>
      <text macro="title"/>
    </substitute>
  </names>
</macro>

Label in `cs:names`

A cs:label element (see label) may optionally be included in cs:names. It must appear before the cs:substitute element. The position of cs:label relative to cs:name determines the order of the name and label in the rendered text. When used as a child element of cs:names, cs:label does not carry the variable attribute; it uses the variable(s) set on the parent cs:names element instead. A second difference is that the form attribute may also be set to "verb" or "verb-short", so that the allowed values are:

"long" - (default), e.g. "editor" and "editors" for the "editor" term
"short" - e.g. "ed." and "eds." for the term "editor"
"verb" - e.g. "edited by" for the term "editor"
"verb-short" - e.g. "ed." for the term "editor"
"symbol" - e.g. "§" and "§§" for the term "section"

Label

The cs:label rendering element outputs the term matching the variable selected with the required variable attribute, which must be set to "locator", "page", or one of the number variables. The term is only rendered if the selected variable is non-empty. For example,

<group delimiter=" ">
  <label variable="page"/>
  <text variable="page"/>
</group>

can result in "page 3" or "pages 5-7". cs:label may carry the following attributes:

form

Selects the form of the term, with allowed values:

"long" - (default), e.g. "page"/"pages" for the "page" term
"short" - e.g. "p."/"pp." for the "page" term
"symbol" - e.g. "§"/"§§" for the "section" term

plural

Sets pluralization of the term, with allowed values:

"contextual" - (default), the term plurality matches that of the variable content. Content is considered plural when it contains multiple numbers (e.g. "page 1", "pages 1-3", "volume 2", "volumes 2 & 4"), or, in the case of the "number-of-pages" and "number-of-volumes" variables, when the number is higher than 1 ("1 volume" and "3 volumes").
"always" - always use the plural form, e.g. "pages 1" and "pages 1-3"
"never" - always use the singular form, e.g. "page 1" and "page 1-3"

cs:label may also carry affixes, formatting, text-case and strip-periods attributes.

Group

The cs:group rendering element must contain one or more rendering elements (with the exception of cs:layout). cs:group may carry the delimiter attribute to separate its child elements, as well as affixes, display, and formatting attributes (applied to the output of the group as a whole). cs:group implicitly acts as a conditional: cs:group and its child elements are suppressed if a) at least one rendering element in cs:group calls a variable (either directly or via a macro), and b) all variables that are called are empty. This accommodates descriptive cs:text and `cs:label`elements. For example,

<layout>
  <group delimiter=" ">
    <text term="retrieved"/>
    <text term="from"/>
    <text variable="URL"/>
  </group>
</layout>

can result in "retrieved from https://doi.org/10.1128/AEM.02591-07", but doesn't generate output when the "URL" variable is empty.

If a cs:group is nested within another cs:group, the inner group is evaluated first: a non-empty nested cs:group is treated as a non-empty variable for the puropses of determining suppression of the outer cs:group.

When a cs:group contains a child cs:macro, if the cs:macro is non-empty, it is treated as a non-empty variable for the purposes of determining suppression of the outer cs:group.

Choose

The cs:choose rendering element allows for conditional rendering of rendering elements. An example that renders the "issued" date variable when it exists, and the "no date" term when it doesn't:

<choose>
  <if variable="issued">
    <date variable="issued" form="numeric"/>
  </if>
  <else>
    <text term="no date"/>
  </else>
</choose>

cs:choose requires a cs:if child element, which may be followed by one or more cs:else-if child elements, and an optional closing cs:else child element. The cs:if and cs:else-if elements may contain any number of rendering elements (except for cs:layout). As an empty cs:else element would be superfluous, cs:else must contain at least one rendering element. cs:if and cs:else-if elements must carry one or more conditions, which are set with the attributes:

disambiguate

When set to "true" (the only allowed value), the element content is only rendered if it disambiguates two otherwise identical citations. This attempt at disambiguation is only made when all other disambiguation methods have failed to uniquely identify the target source.

is-numeric

Tests whether the given variables (Appendix IV - Variables) contain numeric content. Content is considered numeric if it solely consists of numbers. Numbers may have prefixes and suffixes ("D2", "2b", "L2d"), and may be separated by a comma, hyphen, or ampersand, with or without spaces ("2, 3", "2-4", "2 & 4"). For example, "2nd" tests "true" whereas "second" and "2nd edition" test "false".

is-uncertain-date

Tests whether the given date variables contain approximate dates.

locator

Tests whether the locator matches the given locator types (see Locators). Use "sub-verbo" to test for the "sub verbo" locator type.

position

Tests whether the cite position matches the given positions (terminology: citations consist of one or more cites to individual items). When called within the scope of cs:bibliography, position tests "false". The positions that can be tested are:

"first": position of cites that are the first to reference an item
"ibid"/"ibid-with-locator"/"subsequent": cites referencing previously cited items have the "subsequent" position. Such cites may also have the "ibid" or "ibid-with-locator" position when:
1. the current cite immediately follows on another cite, within the same citation, that references the same item
or
1. the current cite is the first cite in the citation, and the previous citation consists of a single cite referencing the same item
If either requirement is met, the presence of locators determines which position is assigned:
- Preceding cite does not have a locator: if the current cite has a locator, the position of the current cite is "ibid-with-locator". Otherwise the position is "ibid".
- Preceding cite does have a locator: if the current cite has the same locator, the position of the current cite is "ibid". If the locator differs the position is "ibid-with-locator". If the current cite lacks a locator its only position is "subsequent".
"near-note": position of a cite following another cite referencing the same item. Both cites have to be located in foot or endnotes, and the distance between both cites may not exceed the maximum distance (measured in number of foot or endnotes) set with the near-note-distance option (see Note Distance).

Whenever position="ibid-with-locator" tests true, position="ibid" also tests true. And whenever position="ibid" or position="near-note" test true, position="subsequent" also tests true.

type

Tests whether the item matches the given types (Appendix III - Types).

variable

Tests whether the default (long) forms of the given variables (Appendix IV - Variables) contain non-empty values.

With the exception of disambiguate, all conditions allow for multiple test values (separated with spaces, e.g. "book thesis").

The cs:if and cs:else-if elements may carry the match attribute to control the testing logic, with allowed values:

"all" - (default), element only tests "true" when all conditions test "true" for all given test values
"any" - element tests "true" when any condition tests "true" for any given test value
"none" - element only tests "true" when none of the conditions test "true" for any given test value

Delimiters from the nearest delimiters from the nearest ancestor delimiting element are applied within the output of cs:choose (i.e., the output of the matching cs:if, cs:else-if, or cs:else; see delimiter).

Style Behavior

Options

Styles may be configured with citation-specific options, set as attributes on set on cs:citation, bibliography-specific options, set on cs:bibliography, and global options (these affect both citations and the bibliography), set on cs:style. Inheritable name options may be set on cs:style, cs:citation and cs:bibliography. Finally, locale options may be set on cs:locale elements.

Citation-specific Options

Disambiguation

A cite is ambiguous when it matches multiple bibliographic entries [1]. Four methods are available to eliminate such ambiguity, which are always tried in the following order:

Expand names (adding initials or full given names)
Show more names
Render the cite with the disambiguate attribute of cs:choose conditions testing "true"
Add a year-suffix

Method 1 can also be used for the separate purpose of global name disambiguation, covering both ambiguous and unambiguous cites throughout the document.

The four disambiguation methods can be individually activated with the following optional attributes:

disambiguate-add-givenname [Method (1)]

If set to "true" ("false" is the default), ambiguous names (names that are identical in their "short" or initialized "long" form, but differ when initials are added or the full given name is shown) are expanded. Name expansion can be configured with givenname-disambiguation-rule. An example of cite disambiguation:

Original ambiguous cites	Disambiguated cites
(Simpson 2005; Simpson 2005)	(H. Simpson 2005; B. Simpson 2005)
(Doe 1950; Doe 1950)	(John Doe 1950; Jane Doe 1950)

givenname-disambiguation-rule

Specifies (a) whether the purpose of name expansion is limited to disambiguating cites, or has the additional goal of disambiguating names (only in the latter case are ambiguous names in unambiguous cites expanded, e.g. from "(Doe 1950; Doe 2000)" to "(Jane Doe 1950; John Doe 2000)"), (b) whether name expansion targets all, or just the first name of each cite, and (c) the method by which each name is expanded.

Expansion of Individual Names

The steps for expanding individual names are:

If initialize-with is set and initialize has its default value of "true", then:

(a) Initials can be shown by rendering the name with a form value of "long" instead of "short" (e.g. "Doe" becomes "J. Doe").

(b) Full given names can be shown instead of initials by rendering the name with initialize set to "false" (e.g. "J. Doe" becomes "John Doe").
If initialize-with is not set, full given names can be shown by rendering the name with a form value of "long" instead of "short" (e.g. "Doe" becomes "John Doe").

Given Name Disambiguation Rules

Allowed values of givenname-disambiguation-rule:

"all-names": Name expansion has the dual purpose of disambiguating cites and names. All rendered ambiguous names, in both ambiguous and unambiguous cites, are subject to disambiguation. Each name is progressively transformed until it is disambiguated. Names that cannot be disambiguated remain in their original form.
"all-names-with-initials": As "all-names", but name expansion is limited to showing initials (see step 1(a) above). No disambiguation attempt is made when initialize-with is not set or when initialize is set to "false".
"primary-name": As "all-names", but disambiguation is limited to the first name of each cite.
"primary-name-with-initials": As "all-names-with-initials", but disambiguation is limited to the first name of each cite.
"by-cite": Default. As "all-names", but the goal of name expansion is limited to disambiguating cites. Only ambiguous names in ambiguous cites are affected, and disambiguation stops after the first name that eliminates cite ambiguity.

disambiguate-add-names [Method (2)]

If set to "true" ("false" is the default), names that would otherwise be hidden as a result of et-al abbreviation are added one by one to all members of a set of ambiguous cites, until no more cites in the set can be disambiguated by adding names.

If both disambiguate-add-givenname and disambiguate-add-names are set to "true", given name expansion is applied to rendered names first. If cites cannot be (fully) disambiguated by expanding the rendered names, then the names still hidden as a result of et-al abbreviation are added one by one to all members of a set of ambiguous cites. Added names are expanded if doing so would disambiguate the ambiguous cites. This process contines until no more cites in the set can be disambiguated by adding expanded names.

In the description of disambiguation methods (1) and (2) above, we assumed that each (disambiguated) cite has an unambiguous link to its bibliographic entry. To assure that each cite does in fact uniquely identify its entry in the bibliography, detail that distinguishes cites (such as names, initials, and full given names) must be shown in the corresponding bibliography entries. If this is not the case, disambiguation methods (1) and (2) also act on all members of a set of ambiguously cited bibliographic entries, until no more entries in the set can be unambiguously cited by adding (expanded) names. Each method only takes effect on the involved bibliographic entries after it has been used to disambiguate cites.

disambiguate condition [Method (3)]: A disambiguation attempt can also be made by rendering ambiguous cites with the disambiguate condition testing "true" (see Choose).
disambiguate-add-year-suffix [Method (4)]: If set to "true" ("false" is the default), an alphabetic year-suffix is added to ambiguous cites (e.g. "Doe 2007, Doe 2007" becomes "Doe 2007a, Doe 2007b") and to their corresponding bibliographic entries. This final disambiguation method is always successful. The assignment of year-suffixes follows the order of the bibliographies entries, and additional letters are used once "z" is reached ("z", "aa", "ab", ..., "az", "ba", etc.). By default, the year-suffix is appended the first year rendered through cs:date in the cite and in the bibliographic entry, but its location can be controlled by explicitly rendering the "year-suffix" variable using cs:text. If "year-suffix" is rendered through cs:text in the scope of cs:citation, it is suppressed for cs:bibliography, unless it is also rendered through cs:text in the scope of cs:bibliography, and vice versa.

[1]	Including uncited entries in the bibliography can make cites in the document ambiguous. To make sure such cites are disambiguated, the CSL processor should include (invisible) cites for such uncited bibliographic entries in the disambiguation process.

Cite Grouping

With cite grouping, cites in in-text citations with identical rendered names are grouped together, e.g. the year-sorted "(Doe 1999; Smith 2002; Doe 2006; Doe et al. 2007)" becomes "(Doe 1999; Doe 2006; Smith 2002; Doe et al. 2007)". The comparison is limited to the output of the (first) cs:names element, but includes output rendered through cs:substitute. Cite grouping takes places after cite sorting and disambiguation. Grouped cites maintain their relative order, and are moved to the original location of the first cite of the group.

Cite grouping can be activated by setting the cite-group-delimiter attribute or the collapse attributes on cs:citation (see also Cite Collapsing).

cite-group-delimiter: Activates cite grouping and specifies the delimiter for cites within a cite group. Defaults to ", ". E.g. with delimiter on cs:layout in cs:citation set to "; ", collapse set to "year", and cite-group-delimiter set to ",", citations look like "(Doe 1999,2001; Jones 2000)".

Cite Collapsing

Cite groups (author and author-date styles), and numeric cite ranges (numeric styles) can be collapsed through the use of the collapse attribute. Delimiters for collapsed cite groups can be customized with the year-suffix-delimiter and after-collapse-delimiter attributes:

collapse

Activates cite grouping and collapsing. Allowed values:

"citation-number" - collapses ranges of cite numbers (rendered through the "citation-number" variable) in citations for "numeric" styles (e.g. from "[1, 2, 3, 5]" to "[1–3, 5]"). Only increasing ranges collapse, e.g. "[3, 2, 1]" will not collapse (to see how to sort cites by "citation-number", see Sorting).
"year" - collapses cite groups by suppressing the output of the cs:names element for subsequent cites in the group, e.g. "(Doe 2000, Doe 2001)" becomes "(Doe 2000, 2001)".
"year-suffix" - collapses as "year", but also suppresses repeating years within the cite group, e.g. "(Doe 2000a, b)" instead of "(Doe 2000a, 2000b)".
"year-suffix-ranged" - collapses as "year-suffix", but also collapses ranges of year-suffixes, e.g. "(Doe 2000a–c,e)" instead of "(Doe 2000a, b, c, e)".

"year-suffix" and "year-suffix-ranged" fall back to "year" when disambiguate-add-year-suffix is "false" (see Disambiguation), or when a cite has a locator (e.g. "(Doe 2000a-c, 2000d, p. 5, 2000e,f)", where the cite for "Doe 2000d" has a locator that prevents the cite from further collapsing).

year-suffix-delimiter

Specifies the delimiter for year-suffixes. Defaults to the delimiter set on cs:layout in cs:citation. E.g. with collapse set to "year-suffix", delimiter on cs:layout in cs:citation set to "; ", and year-suffix-delimiter set to ",", citations look like "(Doe 1999a,b; Jones 2000)".

after-collapse-delimiter

Specifies the cite delimiter to be used after a collapsed cite group. Defaults to the delimiter set on cs:layout in cs:citation. E.g. with collapse set to "year", delimiter on cs:layout in cs:citation set to ", ", and after-collapse-delimiter set to "; ", citations look like "(Doe 1999, 2001; Jones 2000, Brown 2001)".

Note Distance

near-note-distance: A cite tests true for the "near-note" position (see Choose) when a preceding note exists that a) refers to the same item and b) does not precede the current note by more footnotes or endnotes than the value of near-note-distance (default value is "5").

Bibliography-specific Options

Whitespace

hanging-indent

If set to "true" ("false" is the default), bibliographic entries are rendered with hanging-indents.

second-field-align

If set, subsequent lines of bibliographic entries are aligned along the second field. With "flush", the first field is flush with the margin. With "margin", the first field is put in the margin, and subsequent lines are aligned with the margin. An example, where the first field is <text variable="citation-number" suffix=". "/>:

9.  Adams, D. (2002). The Ultimate Hitchhiker's Guide to the
    Galaxy (1st ed.).
10. Asimov, I. (1951). Foundation.

line-spacing

Specifies vertical line distance. Defaults to "1" (single-spacing), and can be set to any positive integer to specify a multiple of the standard unit of line height (e.g. "2" for double-spacing).

entry-spacing

Specifies vertical distance between bibliographic entries. By default (with a value of "1"), entries are separated by a single additional line-height (as set by the line-spacing attribute). Can be set to any non-negative integer to specify a multiple of this amount.

Reference Grouping

subsequent-author-substitute

If set, the value of this attribute replaces names in a bibliographic entry that also occur in the preceding entry. The exact method of substitution depends on the value of the subsequent-author-substitute-rule attribute. Substitution is limited to the names of the first cs:names element rendered.

subsequent-author-substitute-rule

Specifies when and how names are substituted as a result of subsequent-author-substitute. Allowed values:

"complete-all" - (default), when all names of the name variable match those in the preceding bibliographic entry, the value of subsequent-author-substitute replaces the entire name list (including punctuation and terms like "et al" and "and"), except for the affixes set on the cs:names element.
"complete-each" - requires a complete match like "complete-all", but now the value of subsequent-author-substitute substitutes for each rendered name.
"partial-each" - when one or more rendered names in the name variable match those in the preceding bibliographic entry, the value of subsequent-author-substitute substitutes for each matching name. Matching starts with the first name, and continues up to the first mismatch.
"partial-first" - as "partial-each", but substitution is limited to the first name of the name variable.

For example, take the following bibliographic entries:

Doe. 1999.
Doe. 2000.
Doe, Johnson & Williams. 2001.
Doe & Smith. 2002.
Doe, Stevens & Miller. 2003.
Doe, Stevens & Miller. 2004.
Doe, Williams et al. 2005.
Doe, Williams et al. 2006.

With subsequent-author-substitute set to "---", and subsequent-author-substitute-rule set to "complete-all", this becomes:

Doe. 1999.
---. 2000.
Doe, Johnson & Williams. 2001.
Doe & Smith. 2002.
Doe, Stevens & Miller. 2003.
---. 2004.
Doe, Williams et al. 2005.
---. 2005.

With subsequent-author-substitute-rule set to "complete-each", this becomes:

Doe. 1999.
---. 2000.
Doe, Johnson & Williams. 2001.
Doe & Smith. 2002.
Doe, Stevens & Miller. 2003.
---, --- & ---. 2004.
Doe, Williams et al. 2005.
---, --- et al. 2006.

With subsequent-author-substitute-rule set to "partial-each", this becomes:

Doe. 1999.
---. 2000.
Doe, Johnson & Williams. 2001.
--- & Smith. 2002.
Doe, Stevens & Miller. 2003.
---, --- & ---. 2004.
Doe, Williams et al. 2005.
---, --- et al. 2005.

With subsequent-author-substitute-rule set to "partial-first", this becomes:

Doe. 1999.
---. 2000.
Doe, Johnson & Williams. 2001.
--- & Smith. 2002.
Doe, Stevens & Miller. 2003.
---, Stevens & Miller. 2004.
Doe, Williams et al. 2005.
---, Williams et al. 2005.

Global Options

Hyphenation of Initialized Names

initialize-with-hyphen: Specifies whether compound given names (e.g. "Jean-Luc") should be initialized with a hyphen ("J.-L.", value "true", default) or without ("J. L.", value "false").

Page Ranges

page-range-format: Activates expansion or collapsing of page ranges: "chicago" ("321–28"), "expanded" (e.g. "321–328"), "minimal" ("321–8"), or "minimal-two" ("321–28") (see also Appendix V - Page Range Formats). Delimits page ranges with the "page-range-delimiter" term (introduced with CSL 1.0.1, and defaults to an en-dash). If the attribute is not set, page ranges are rendered without reformatting.

Name Particles

Western names frequently contain one or more name particles (e.g. "van" in the Dutch name "Vincent van Gogh"). These name particles can be either kept or dropped when only the surname is shown: these two types are referred to as non-dropping and dropping particles, respectively. Theoretically, a single name might contain particles of both types (with non-dropping particles always following dropping particles), though currently we are not aware of any real-life examples. For example, the Dutch name "Vincent van Gogh", the German name "Alexander von Humboldt", and the Arabic name "Tawfiq al-Hakim" can be deconstructed into:

{
    "author": [
        {
            "given": "Vincent",
            "non-dropping-particle": "van",
            "family": "Gogh"
        },
        {
            "given": "Alexander",
            "dropping-particle": "von",
            "family": "Humboldt"
        }
        {
            "given": "Tawfiq",
            "non-dropping-particle": "al-",
            "family": "Hakim"
        }
    ]
}

When just the surname is shown, only the non-dropping-particle is kept: "Van Gogh" and "al-Hakim", but "Humboldt".

In the case of inverted names, where the family name precedes the given name, the dropping-particle is always appended to the family name, but the non-dropping-particle can be either prepended (e.g. "van Gogh, Vincent") or appended (after initials or given names, e.g. "Gogh, Vincent van"). For inverted names where the non-dropping-particle is prepended, names can either be sorted by keeping the non-dropping-particle together with the family name as part of the primary sort key (sort order A), or by separating the non-dropping-particle from the family name and have it become (part of) a secondary sort key, joining the dropping-particle, if available (sort order B):

Sort order A: non-dropping-particle not demoted

primary sort key: "van Gogh"
secondary sort key: ""
tertiary sort key: "Vincent"

Sort order B: non-dropping-particle demoted

primary sort key: "Gogh"
secondary sort key: "van"
tertiary sort key: "Vincent"

The handling of the non-dropping-particle can be customized with the demote-non-dropping-particle option:

demote-non-dropping-particle

Sets the display and sorting behavior of the non-dropping-particle in inverted names (e.g. "Gogh, Vincent van"). Allowed values:

"never": the non-dropping-particle is treated as part of the family name, whereas the dropping-particle is appended (e.g. "van Gogh, Vincent", "Humboldt, Alexander von"). The non-dropping-particle is part of the primary sort key (sort order A, e.g. "van Gogh, Vincent" appears under "V").
"sort-only": same display behavior as "never", but the non-dropping-particle is demoted to a secondary sort key (sort order B, e.g. "van Gogh, Vincent" appears under "G").
"display-and-sort" (default): the dropping and non-dropping-particle are appended (e.g. "Gogh, Vincent van" and "Humboldt, Alexander von"). For name sorting, all particles are part of the secondary sort key (sort order B, e.g. "Gogh, Vincent van" appears under "G").

Some names include a particle that should never be demoted. For these cases the particle should just be included in the family name field, for example for the French general Charles de Gaulle and the writer Jean de La Fontaine:

{
    "author": [
        {
            "given": "Charles"
            "family": "de Gaulle",
        },
        {
            "given": "Jean"
            "dropping-particle": "de",
            "family": "La Fontaine",
        }
    ]
}

Inheritable Name Options

Attributes for the cs:names and cs:name elements may also be set on cs:style, cs:citation and cs:bibliography. This eliminates the need to repeat the same attributes and attribute values for every occurrence of the cs:names and cs:name elements.

The available inheritable attributes for cs:name are and, delimiter-precedes-et-al, delimiter-precedes-last, et-al-min, et-al-use-first, et-al-use-last, et-al-subsequent-min, et-al-subsequent-use-first, initialize, initialize-with, name-as-sort-order and sort-separator. The attributes name-form and name-delimiter correspond to the form and delimiter attributes on cs:name. Similarly, names-delimiter corresponds to the delimiter attribute on cs:names.

When an inheritable name attribute is set on cs:style, cs:citation or cs:bibliography, its value is used for all cs:names elements within the scope of the element carrying the attribute. If an attribute is set on multiple hierarchical levels, the value set at the lowest level is used.

Locale Options

limit-day-ordinals-to-day-1: Date formats are defined by the cs:date element and its cs:date-part child elements (see Date). By default, when the cs:date-part element with name set to "day" has form set to "ordinal", all days (1 through 31) are rendered in the ordinal form, e.g. "January 1st", "January 2nd", etc. By setting limit-day-ordinals-to-day-1 to "true" ("false" is the default), the "ordinal" form is limited to the first day of each month (other days will use the "numeric" form). This is desirable for some languages, such as French: "1er janvier", but "2 janvier", "3 janvier", etc.
punctuation-in-quote: For cs:text elements rendered with the quotes attribute set to "true" (see Formatting), and for which the output is followed by a comma or period, punctuation-in-quote specifies whether this punctuation is placed outside (value "false", default) or inside (value "true") the closing quotation mark.

Sorting

cs:citation and cs:bibliography may include a cs:sort child element before the cs:layout element to specify the sorting order of respectively cites within citations, and bibliographic entries within the bibliography. In the absence of cs:sort, cites and bibliographic entries appear in the order in which they are cited.

The cs:sort element must contain one or more cs:key child elements. The sort key, set as an attribute on cs:key, must be a variable (see Appendix IV - Variables) or macro name. For each cs:key element, the sort direction can be set to either "ascending" (default) or "descending" with the sort attribute. Sorting is case-insensitive. The attributes names-min, names-use-first, and names-use-last may be used to override the values of the corresponding et-al-min/et-al-subsequent-min, et-al-use-first/et-al-subsequent-use-first and et-al-use-last attributes, and affect all names generated via macros called by cs:key.

Sort keys are evaluated in sequence. A primary sort is performed on all items using the first sort key. A secondary sort, using the second sort key, is applied to items sharing the first sort key value. A tertiary sort, using the third sort key, is applied to items sharing the first and second sort key values. Sorting continues until either the order of all items is fixed, or until the sort keys are exhausted. Items with an empty sort key value are placed at the end of the sort, both for ascending and descending sorts.

An example, where cites are first sorted by the output of the "author" macro, with overriding settings for et-al abbreviation. Cites sharing the primary sort key are subsequently sorted in descending order by the "issued" date variable.

<citation>
  <sort>
    <key macro="author" names-min="3" names-use-first="3"/>
    <key variable="issued" sort="descending"/>
  </sort>
  <layout>
    <!-- rendering elements -->
  </layout>
</citation>

The sort key value of a variable or macro can differ from the "normal" rendered output. The specifics of sorting variables and macros:

Sorting Variables

The sort key value for a variable called by cs:key via the variable attribute consists of the string value, without rich text markup. Exceptions are name, date and numeric variables:

names: Name variables called via the variable attribute (e.g. <key variable="author"/>) are returned as a name list string, with the cs:name attributes form set to "long", and name-as-sort-order set to "all".

dates: Date variables called via the variable attribute are returned in the YYYYMMDD format, with zeros substituted for any missing date-parts (e.g. 20001200 for December 2000). As a result, less specific dates precede more specific dates in ascending sorts, e.g. "2000, May 2000, May 1st 2000". Negative years are sorted inversely, e.g. "100BC, 50BC, 50AD, 100AD". Seasons are ignored for sorting, as the chronological order of the seasons differs between the northern and southern hemispheres. In the case of date ranges, the start date is used for the primary sort, and the end date is used for a secondary sort, e.g. "2000–2001, 2000–2005, 2002–2003, 2002–2009". Date ranges are placed after single dates when they share the same (start) date, e.g. "2000, 2000–2002".

numbers: Number variables called via the variable attribute are returned as integers (form is "numeric"). If the original variable value only consists of non-numeric text, the value is returned as a text string.

Sorting Macros

The sort key value for a macro called via cs:key via the macro attribute generally consists of the string value the macro would ordinarily generate, without rich text markup (exceptions are discussed below).

When sorting by name variables rendered within the macro, any cs:label elements are excluded from the sort key values. Name variables are also returned with the cs:name attribute name-as-sort-order set to "all". When et-al abbreviation occurs, the "et-al" and "and others" terms are excluded from the sort key values.

There are four advantages in using the same macro for rendering and sorting, instead of sorting directly on the name variable. First, substitution is available (e.g. the "editor" variable might substitute for an empty "author" variable). Second, et-al abbreviation can be used (using either the et-al-min/et-al-subsequent-min, et-al-use-first/et-al-subsequent-use-first, and et-al-use-last options defined for the macro, or the overriding names-min, names-use-first and names-use-last attributes set on cs:key). Third, names can be sorted by just the surname (using a macro for which the form attribute on cs:name is set to "short"). Fourth, it is possible to sort by the number of names in a name list, by calling a macro for which the form attribute on cs:name is set to "count".

Number variables rendered within the macro with cs:number and date variables are treated the same as when they are called via variable. The only exception is that the complete date is returned if a date variable is called via the variable attribute. In contrast, macros return only those date-parts that would otherwise be rendered (respecting the value of the date-parts attribute for localized dates, or the listing of cs:date-part elements for non-localized dates).

Range Delimiters

Collapsed ranges for the "citation-number" and "year-suffix" variables are delimited by an en-dash (e.g. "(1–3, 5)" and "(Doe 2000a–c,e)").

The "locator" variable is always rendered with an en-dash replacing any hyphens. For the "page" variable, this replacement is only performed if the page-range-format attribute is set on cs:style (see Page Ranges).

Formatting

The following formatting attributes may be set on cs:date, cs:date-part, cs:et-al, cs:group, cs:label, cs:layout, cs:name, cs:name-part, cs:names, cs:number and cs:text:

font-style

Sets the font style, with values:

"normal" (default)
"italic"
"oblique" (i.e. slanted)

font-variant

Allows for the use of small capitals, with values:

"normal" (default)
"small-caps"

font-weight

Sets the font weight, with values:

"normal" (default)
"bold"
"light"

text-decoration

Allows for the use of underlining, with values:

"none" (default)
"underline"

vertical-align

Sets the vertical alignment, with values:

"baseline" (default)
"sup" (superscript)
"sub" (subscript)

Affixes

The affixes attributes prefix and suffix may be set on cs:date (except when cs:date defines a localized date format), cs:date-part (except when the parent cs:date element calls a localized date format), cs:group, cs:label, cs:layout, cs:name, cs:name-part, cs:names, cs:number and cs:text. The attribute value is either added before (prefix) or after (suffix) the output of the element carrying the attribute, but affixes are only rendered if the element produces output. With the exception of affixes set on cs:layout, affixes are outside the scope of formatting, quotes, strip-periods and text-case attributes set on the same element (as a workaround, these attributes take effect on affixes when set on a parent cs:group element).

Delimiter

The delimiter attribute, whose value delimits non-empty pieces of output, may be set on cs:date (delimiting the date-parts; delimiter is not allowed when cs:date calls a localized date format), cs:names (delimiting name lists from different name variables), cs:name (delimiting names within name lists), cs:group and cs:layout (delimiting the output of the child elements).

A delimiting element is any element as above which takes a delimiter attribute, whether the attribute is supplied or not.

Delimiters from any ancestor delimiting element are not applied within the output of a delimiting element. The following produces retrieved: <http://example.com>:

<group delimiter=": ">
  <text term="retrieved" />
  <group>
    <text value="&lt;" />
    <text variable="URL" />
    <text value="&gt;" />
  </group>
</group>

Display

The display attribute (similar the "display" property in CSS) may be used to structure individual bibliographic entries into one or more text blocks. If used, all rendering elements should be under the control of a display attribute. The allowed values:

"block" - block stretching from margin to margin.
"left-margin" - block starting at the left margin. If followed by a "right-inline" block, the "left-margin" blocks of all bibliographic entries are set to a fixed width to accommodate the longest content string found among these "left-margin" blocks. In the absence of a "right-inline" block the "left-margin" block extends to the right margin.
"right-inline" - block starting to the right of a preceding "left-margin" block (behaves as "block" in the absence of such a "left-margin" block). Extends to the right margin.
"indent" - block indented to the right by a standard amount. Extends to the right margin.

Examples

Instead of using second-field-align (see Whitespace), a similar layout can be achieved with a "left-margin" and "right-inline" block. A potential benefit is that the styling of blocks can be further controlled in the final output (e.g. using CSS for HTML, styles for Word, etc.).
```
<bibliography>
  <layout>
    <text display="left-margin" variable="citation-number"
        prefix="[" suffix="]"/>
    <group display="right-inline">
      
    </group>
  </layout>
</bibliography>
```

A per-author publication listing. With subsequent-author-substitute (see Reference Grouping) set to an empty string, the block with the author names is only rendered once for items by the same authors.

<bibliography subsequent-author-substitute="">
  <sort>
    <key variable="author"/>
    <key variable="issued"/>
  </sort>
  <layout>
    <group display="block">
      <names variable="author"/>
    </group>
    <group display="left-margin">
      <date variable="issued">
        <date-part name="year" />
      </date>
    </group>
    <group display="right-inline">
      <text variable="title"/>
    </group>
  </layout>
</bibliography>

The output of this example would look like:

Author1
year-publication1	title-publication1
year-publication2	title-publication2
Author2
year-publication3	title-publication3
year-publication4	title-publication4

An annotated bibliography, where the annotation appears in an indented block below the reference.

<bibliography>
  <layout>
    <group display="block">
      <!-- rendering elements -->
    </group>
    <text display="indent" variable="abstract" />
  </layout>
</bibliography>

Quotes

The quotes attribute may set on cs:text. When set to "true" ("false" is default), the rendered text is wrapped in quotes (the quotation marks used are terms). The localized punctuation-in-quote option controls whether an adjoining comma or period appears outside (default) or inside the closing quotation mark (see Locale Options).

Strip-periods

The strip-periods attribute may be set on cs:date-part (but only if name is set to "month"), cs:label and cs:text. When set to "true" ("false" is the default), any periods in the rendered text are removed.

Text-case

The text-case attribute may be set on cs:date, cs:date-part, cs:label, cs:name-part, cs:number and cs:text. The allowed values:

"lowercase": renders text in lowercase
"uppercase": renders text in uppercase
"capitalize-first": capitalizes the first character of the first word, if the word is lowercase
"capitalize-all": capitalizes the first character of every lowercase word
"sentence": renders text in sentence case (deprecated; do not use)
"title": renders text in title case

Sentence Case Conversion

Sentence case conversion (with text-case set to "sentence") is performed by:

For uppercase strings, the first character of the string remains capitalized. All other letters are lowercased.
For lower or mixed case strings, the first character of the first word is capitalized if the word is lowercase. The case of all other words stays the same.

CSL processors don't recognize proper nouns. As a result, strings in sentence case can be accurately converted to title case, but not vice versa. For this reason, it is generally preferable to store strings such as titles in sentence case, and only use text-case if a style desires another case.

Sentence case conversion is deprecated and will be removed in a future version.

Title Case Conversion

Title case conversion (with text-case set to "title") for English-language items is performed by:

For uppercase strings, the first character of each word remains capitalized. All other letters are lowercased.
For lower or mixed case strings, the first character of each lowercase word is capitalized. The case of words in mixed or uppercase stays the same.

In both cases, stop words are lowercased, unless they are the first or last word in the string, or follow a colon. The stop words are listed in the CSL Schema file stop-words.json. Hyphenated word parts are treated as distinct words (e.g., "two-thirds" becomes "Two-Thirds").

Non-English Items

As many languages do not use title case, title case conversion (with text-case set to "title") only affects English-language items.

If the default-locale attribute on cs:style isn't set, or set to a locale code with a primary language tag of "en" (English), items are assumed to be English. An item is only considered to be non-English if its metadata contains a language field with a non-nil value that doesn't start with the "en" primary language tag.

If default-locale is set to a locale code with a primary language tag other than "en", items are assumed to be non-English. An item is only considered to be English if the value of its language field starts with the "en" primary language tag.

Appendix II - Terms

Type Terms

For each item type listed in Appendix III - Types, there is a corresponding term.

Name Variable Terms

For each of the Name Variables listed in Appendix IV - Variables, there is a corresponding term.

Number Variable Terms

For each of the Number Variables listed in Appendix IV - Variables, there is a corresponding term.

Locators

act
appendix
article-locator
book
canon
chapter
column
elocation
equation
figure
folio
issue
line
note
opus
page
paragraph
part
rule
scene
section
sub-verbo
supplement
table
timestamp
title-locator
verse
version
volume

Months

month-01
month-02
month-03
month-04
month-05
month-06
month-07
month-08
month-09
month-10
month-11
month-12

Ordinals

ordinal
ordinal-00 through ordinal-99
long-ordinal-01
long-ordinal-02
long-ordinal-03
long-ordinal-04
long-ordinal-05
long-ordinal-06
long-ordinal-07
long-ordinal-08
long-ordinal-09
long-ordinal-10

Punctuation

open-quote
close-quote
open-inner-quote
close-inner-quote
page-range-delimiter
colon
comma
semicolon

Seasons

season-01
season-02
season-03
season-04

Miscellaneous

accessed
ad
advance-online-publication
album
and
and others
anonymous
at
audio-recording
available at
bc
bce
by
ce
circa
cited
et-al
film
forthcoming
from
henceforth
ibid
in
in press
internet
letter
loc-cit
no date
no-place
no-publisher
on
online
op-cit
original-work-published
personal-communication
podcast
podcast-episode
preprint
presented at
radio-broadcast
radio-series
radio-series-episode
reference
retrieved
review-of
scale
special-issue
special-section
television-broadcast
television-series
television-series-episode
video
working-paper

Appendix III - Types

article: A self-contained work made widely available but not published in a journal or other publication;

Use for preprints, working papers, and similar works posted on a platform where some level of persistence or stewardship is expected (e.g. arXiv or other preprint repositories, working paper series);

For unpublished works not made widely available or only hosted on personal websites, use manuscript
article-journal: An article published in an academic journal
article-magazine: An article published in a non-academic magazine
article-newspaper: An article published in a newspaper
bill: A proposed piece of legislation
book: A book or similar work;

Can be an authored book or an edited collection of self-contained chapters;

Can be a physical book or an ebook;

The format for an ebook may be specified using medium;

Can be a single-volume work, a multivolume work, or one volume of a multivolume work;

If a container-title is present, the item is interpreted as a book republished in a collection or anthology;

Also used for whole conference proceedings volumes or exhibition catalogs by specifying event and related variables
broadcast: A recorded work broadcast over an electronic medium (e.g. a radio broadcast, a television show, a podcast);

The type of broadcast may be specified using genre;

If container-title is present, the item is interpreted as an episode contained within a larger broadcast series (e.g. an episode in a television show or an episode of a podcast)
chapter: A part of a book cited separately from the book as a whole (e.g. a chapter in an edited book);

Also used for introductions, forewords, and similar supplemental components of a book
classic: A classical or ancient work, sometimes cited using a common abbreviation
collection: An archival collection in a museum or other institution
dataset: A data set or a similar collection of (mostly) raw data
document: A catch-all category for items not belonging to other types;

Use a more specific type when appropriate
entry: An entry in a database, directory, or catalog;

For entries in a dictionary, use entry-dictionary;

For entries in an encyclopedia, use entry-encyclopedia
entry-dictionary: An entry in a dictionary
entry-encyclopedia: An entry in an encyclopedia or similar reference work
event: An organized event (e.g., an exhibition or conference);

Use for direct citations to the event, rather than to works contained within an event (e.g. a presentation in a conference, a graphic in an exhibition) or based on an event (e.g. a paper-conference published in a proceedings, an exhibition catalog)
figure: A illustration or representation of data, typically as part of a journal article or other larger work;

May be in any format (e.g. image, video, audio recording, 3D model);

The format of the item can be specified using medium
graphic: A still visual work;

Can be used for artwork or other works (e.g. journalistic or historical photographs);

Can be used for any still visual work (e.g. photographs, drawings, paintings, sculptures, clothing);

The format of the item can be specified using medium
hearing: A hearing by a government committee or transcript thereof
interview: An interview of a person;

Also used for a recording or transcript of an interview; author is interpreted as the interviewee
legal_case: A legal case
legislation: A law or resolution enacted by a governing body
manuscript: An unpublished manuscript;

Use for both modern unpublished works and classical manuscripts;

For working papers, preprints, and similar works posted to a repository, use article
map: A geographic map
motion_picture: A video or visual recording;

If a container-title is present, the item is interpreted as a part contained within a larger compilation of recordings (e.g. a part of a multipart documentary))
musical_score: The printed score for a piece of music;

For a live performance of the music, use performance;

For recordings of the music, use song (for audio recordings) or motion_picture (for video recordings)
pamphlet: A fragment, historical document, or other unusually-published or ephemeral work (e.g. a sales brochure)
paper-conference: A paper formally published in conference proceedings;

For papers presented at a conference, but not published in a proceedings, use speech
patent: A patent for an invention
performance: A live performance of an artistic work;

For non-artistic presentations, use speech;

For recordings of a performance, use song or motion_picture
periodical: A full issue or run of issues in a periodical publication (e.g. a special issue of a journal)
personal_communication: Personal communications between multiple parties;

May be unpublished (e.g. private correspondence between two researchers) or collected/published (e.g. a letter published in a collection)
post: A post on a online forum, social media platform, or similar platform;

Also used for comments posted to online items
post-weblog: A blog post
regulation: An administrative order from any level of government
report: A technical report, government report, white paper, brief, or similar work distributed by an institution;

Also used for manuals and similar technical documentation (e.g. a software, instrument, or test manual);

If a container-title is present, the item is interpreted as a chapter contained within a larger report
review: A review of an item other than a book (e.g. a film review, posted peer review of an article);

If reviewed-title is absent, title is taken to be the title of the reviewed item
review-book: A review of a book;

If reviewed-title is absent, title is taken to be the title of the reviewed book
software: A computer program, app, or other piece of software
song: An audio recording;

Can be used for any audio recording (not only music);

If a container-title is present, the item is interpreted as a track contained within a larger album or compilation of recordings
speech: A speech or other presentation (e.g. a paper, talk, poster, or symposium at a conference);

Use genre to specify the type of presentation;

Use event to indicate the event where the presentation was made (e.g. the conference name);

Use container-title if the presentation is part of a larger session (e.g. a paper in a symposium);

For papers published in conference proceedings, use paper-conference;

For artistic performances, use performance
standard: A technical standard or similar set of rules or norms
thesis: A thesis written to satisfy requirements for a degree;

Use genre to specify the type of thesis
treaty: A treaty agreement among political authorities
webpage: A website or page on a website;

Intended for sources which are intrinsically online; use a more specific type when appropriate (e.g. article-journal, post-weblog, report, entry);

If a container-title is present, the item is interpreted as a page contained within a larger website

Appendix IV - Variables

Standard Variables

abstract: Abstract of the item (e.g. the abstract of a journal article)
annote: Short markup, decoration, or annotation to the item (e.g., to indicate items included in a review);

For descriptive text (e.g., in an annotated bibliography), use note instead
archive: Archive storing the item
archive_collection: Collection the item is part of within an archive
archive_location: Storage location within an archive (e.g. a box and folder number)
archive-place: Geographic location of the archive
authority: Issuing or judicial authority (e.g. "USPTO" for a patent, "Fairfax Circuit Court" for a legal case)
call-number: Call number (to locate the item in a library)
citation-key: Identifier of the item in the input data file (analogous to BibTeX entrykey);

Use this variable to facilitate conversion between word-processor and plain-text writing systems;

For an identifer intended as formatted output label for a citation (e.g. "Ferr78"), use citation-label instead
citation-label: Label identifying the item in in-text citations of label styles (e.g. "Ferr78");

May be assigned by the CSL processor based on item metadata;

For the identifier of the item in the input data file, use citation-key instead
collection-title: Title of the collection holding the item (e.g. the series title for a book; the lecture series title for a presentation)
container-title: Title of the container holding the item (e.g. the book title for a book chapter, the journal title for a journal article; the album title for a recording; the session title for multi-part presentation at a conference)
container-title-short: Short/abbreviated form of container-title;

Deprecated; use variable="container-title" form="short" instead
dimensions: Physical (e.g. size) or temporal (e.g. running time) dimensions of the item
division: Minor subdivision of a court with a jurisdiction for a legal item
DOI: Digital Object Identifier (e.g. "10.1128/AEM.02591-07")
event: Deprecated legacy variant of event-title
event-title: Name of the event related to the item (e.g. the conference name when citing a conference paper; the meeting where presentation was made)
event-place: Geographic location of the event related to the item (e.g. "Amsterdam, The Netherlands")
genre: Type, class, or subtype of the item (e.g. "Doctoral dissertation" for a PhD thesis; "NIH Publication" for an NIH technical report);

Do not use for topical descriptions or categories (e.g. "adventure" for an adventure movie)
ISBN: International Standard Book Number (e.g. "978-3-8474-1017-1")
ISSN: International Standard Serial Number
jurisdiction: Geographic scope of relevance (e.g. "US" for a US patent; the court hearing a legal case)
keyword: Keyword(s) or tag(s) attached to the item
language: The language of the item;

Should be entered as an ISO 639-1 two-letter language code (e.g. "en", "zh"), optionally with a two-letter locale code (e.g. "de-DE", "de-AT")
license: The license information applicable to an item (e.g. the license an article or software is released under; the copyright information for an item; the classification status of a document)
medium: Description of the item's format or medium (e.g. "CD", "DVD", "Album", etc.)
note: Descriptive text or notes about an item (e.g. in an annotated bibliography)
original-publisher: Original publisher, for items that have been republished by a different publisher
original-publisher-place: Geographic location of the original publisher (e.g. "London, UK")
original-title: Title of the original version (e.g. "Война и мир", the untranslated Russian title of "War and Peace")
part-title: Title of the specific part of an item being cited
PMCID: PubMed Central reference number
PMID: PubMed reference number
publisher: Publisher
publisher-place: Geographic location of the publisher
references: Resources related to the procedural history of a legal case or legislation;

Can also be used to refer to the procedural history of other items (e.g. "Conference canceled" for a presentation accepted as a conference that was subsequently canceled; details of a retraction or correction notice)
reviewed-genre: Type of the item being reviewed by the current item (e.g. book, film)
reviewed-title: Title of the item reviewed by the current item
scale: Scale of e.g. a map or model
source: Source from whence the item originates (e.g. a library catalog or database)
status: Publication status of the item (e.g. "forthcoming"; "in press"; "advance online publication"; "retracted")
title: Primary title of the item
title-short: Short/abbreviated form of title;

Deprecated; use variable="title" form="short" instead
URL: Uniform Resource Locator (e.g. "https://aem.asm.org/cgi/content/full/74/9/2766")
volume-title: Title of the volume of the item or container holding the item;

Also use for titles of periodical special issues, special sections, and the like
year-suffix: Disambiguating year suffix in author-date styles (e.g. "a" in "Doe, 1999a")

Number Variables

Number variables are a subset of the Standard Variables.

chapter-number: Chapter number (e.g. chapter number in a book; track number on an album)
citation-number: Index (starting at 1) of the cited reference in the bibliography (generated by the CSL processor)
collection-number: Number identifying the collection holding the item (e.g. the series number for a book)
edition: (Container) edition holding the item (e.g. "3" when citing a chapter in the third edition of a book)
first-reference-note-number: Number of a preceding note containing the first reference to the item;

Assigned by the CSL processor;

Empty in non-note-based styles or when the item hasn't been cited in any preceding notes in a document
issue: Issue number of the item or container holding the item (e.g. "5" when citing a journal article from journal volume 2, issue 5);

Use volume-title for the title of the issue, if any
locator: A cite-specific pinpointer within the item (e.g. a page number within a book, or a volume in a multi-volume work);

Must be accompanied in the input data by a label indicating the locator type (see the Locators term list), which determines which term is rendered by cs:label when the locator variable is selected.
number: Number identifying the item (e.g. a report number)
number-of-pages: Total number of pages of the cited item
number-of-volumes: Total number of volumes, used when citing multi-volume books and such
page: Range of pages the item (e.g. a journal article) covers in a container (e.g. a journal issue)
page-first: First page of the range of pages the item (e.g. a journal article) covers in a container (e.g. a journal issue)
part-number: Number of the specific part of the item being cited (e.g. part 2 of a journal article);

Use part-title for the title of the part, if any
printing-number: Printing number of the item or container holding the item
section: Section of the item or container holding the item (e.g. "§2.0.1" for a law; "politics" for a newspaper article)
supplement-number: Supplement number of the item or container holding the item (e.g. for secondary legal items that are regularly updated between editions)
version: Version of the item (e.g. "2.0.9" for a software program)
volume: Volume number of the item (e.g. "2" when citing volume 2 of a book) or the container holding the item (e.g. "2" when citing a chapter from volume 2 of a book);

Use volume-title for the title of the volume, if any

Date Variables

accessed: Date the item has been accessed
available-date: Date the item was initially available (e.g. the online publication date of a journal article before its formal publication date; the date a treaty was made available for signing)
event-date: Date the event related to an item took place
issued: Date the item was issued/published
original-date: Issue date of the original version
submitted: Date the item (e.g. a manuscript) was submitted for publication

Name Variables

author: Author
chair: The person leading the session containing a presentation (e.g. the organizer of the container-title of a speech)
collection-editor: Editor of the collection holding the item (e.g. the series editor for a book)
compiler: Person compiling or selecting material for an item from the works of various persons or bodies (e.g. for an anthology)
composer: Composer (e.g. of a musical score)
container-author: Author of the container holding the item (e.g. the book author for a book chapter)
contributor: A minor contributor to the item; typically cited using "with" before the name when listed in a bibliography
curator: Curator of an exhibit or collection (e.g. in a museum)
director: Director (e.g. of a film)
editor: Editor
editorial-director: Managing editor ("Directeur de la Publication" in French)
editor-translator: Combined editor and translator of a work;

The citation processory must be automatically generate if editor and translator variables are identical;

May also be provided directly in item data
executive-producer: Executive producer (e.g. of a television series)
guest: Guest (e.g. on a TV show or podcast)
host: Host (e.g. of a TV show or podcast)
illustrator: Illustrator (e.g. of a children's book or graphic novel)
interviewer: Interviewer (e.g. of an interview)
narrator: Narrator (e.g. of an audio book)
organizer: Organizer of an event (e.g. organizer of a workshop or conference)
original-author: The original creator of a work (e.g. the form of the author name listed on the original version of a book; the historical author of a work; the original songwriter or performer for a musical piece; the original developer or programmer for a piece of software; the original author of an adapted work such as a book adapted into a screenplay)
performer: Performer of an item (e.g. an actor appearing in a film; a muscian performing a piece of music)
producer: Producer (e.g. of a television or radio broadcast)
recipient: Recipient (e.g. of a letter)
reviewed-author: Author of the item reviewed by the current item
script-writer: Writer of a script or screenplay (e.g. of a film)
series-creator: Creator of a series (e.g. of a television series)
translator: Translator

Appendix V - Page Range Formats

The page abbreviation rules for the different values of the page-range-format attribute on cs:style are:

"chicago"

Alias for "chicago-15"; will change to be an alias for "chicago-16" in CSL v1.1.

"chicago-15"

Page ranges are abbreviated according to the `Chicago Manual of Style (15th ed and earlier) rules`_ (see 15th ed, section 9.64):

First number	Second number	Examples
Less than 100	Use all digits	3–10; 71–72
100 or multiple of 100	Use all digits	100–104; 600–613; 1100–1123
101 through 109 (in multiples of 100)	Use changed part only, omitting unneeded zeros	107–8; 505–17; 1002–6
110 through 199 (in multiples of 100)	Use two digits, or more as needed	321–25; 415–532; 11564–68; 13792–803
4 digits	If numbers are four digits long and three digits change, use all digits	1496–1504; 2787–2816

"chicago-16"

Page ranges are abbreviated according to the Chicago Manual of Style (16th ed and later) rules (see 16th ed, section 9.61):

First number	Second number	Examples
Less than 100	Use all digits	3–10; 71–72; 92–113;
100 or multiple of 100	Use all digits	100–104; 600–613; 1100–1123
101 through 109, 201 through 209, etc. (for each multiple of 100)	Use changed part only, omitting unneeded zeros	107–8; 505–17; 1002–6
Everything else (110 through 199, 210 through 299, etc.; for each multiple of 100)	Use two digits, unless more digits are needed to show the changed part	321–25; 415–532; 1087–89; 1496–500; 11564–68; 13792–803 12991–3001

"expanded"

Abbreviated page ranges are expanded to their non-abbreviated form: 42–45, 321–328, 2787–2816

"minimal"

All digits repeated in the second number are left out: 42–5, 321–8, 2787–816

"minimal-two"

As "minimal", but at least two digits are kept in the second number when it has two or more digits long.

Appendix VI: Links

The CSL syntax does not have support for configuration of links. However, processors should include links on bibliographic references, using the following rules:

If the bibliography entry for an item renders any of the following identifiers, the identifier should be anchored as a link, with the target of the link as follows:

url: output as is
doi: prepend with "https://doi.org/"
pmid: prepend with "https://www.ncbi.nlm.nih.gov/pubmed/"
pmcid: prepend with "https://www.ncbi.nlm.nih.gov/pmc/articles/"

If the identifier is rendered as a URI, include rendered URI components (e.g. "https://doi.org/") in the link anchor. Do not include any other affix text in the link anchor (e.g. "Available from: ", "doi: ", "PMID: ").

Citation processors should include an option flag for calling applications to disable bibliography linking behavior.

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CSL 1.0.2 Specification