diff --git a/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBA.java b/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBA.java
index 3533d2d..7804886 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBA.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBA.java
@@ -5,24 +5,23 @@
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Set;
 
 public final class GNBA {
 
   private static final Gson GSON;
-  private final List<String> states;
-  private final List<String> alphabet;
-  private final List<String> initialStates;
-  private final List<List<String>> acceptingSets;
-  private final List<NBATransition> transitions;
+  private final Set<String> states;
+  private final Set<String> alphabet;
+  private final Set<String> initialStates;
+  private final Set<Set<String>> acceptingSets;
+  private final Set<NBATransition> transitions;
 
   public GNBA(
-      List<String> states,
-      List<String> alphabet,
-      List<String> initialStates,
-      List<List<String>> acceptingSets,
-      List<NBATransition> transitions) {
+      Set<String> states,
+      Set<String> alphabet,
+      Set<String> initialStates,
+      Set<Set<String>> acceptingSets,
+      Set<NBATransition> transitions) {
     this.states = states;
     this.alphabet = alphabet;
     this.initialStates = initialStates;
@@ -79,7 +78,7 @@ public NBA convertToNBA() {
     }
 
     if (!acceptingSets.isEmpty()) {
-      List<String> acceptingSet = acceptingSets.get(0);
+      Set<String> acceptingSet = acceptingSets.stream().findFirst().get();
       for (String acceptingState : acceptingSet) {
         String nbaAcceptingState = stringTuple(acceptingState, 1);
         builder.addAcceptingState(nbaAcceptingState);
@@ -87,8 +86,8 @@ public NBA convertToNBA() {
     }
 
     for (NBATransition transition : transitions) {
-      for (int i = 0; i < acceptingSets.size(); i++) {
-        List<String> acceptingSet = acceptingSets.get(i);
+      int i = 0;
+      for (Set<String> acceptingSet : acceptingSets) {
         String nbaFrom = stringTuple(transition.getFrom(), i + 1);
         String nbaTo;
         if (acceptingSet.contains(transition.getFrom())) {
@@ -97,6 +96,8 @@ public NBA convertToNBA() {
           nbaTo = stringTuple(transition.getTo(), (i + 1));
         }
         builder.addTransition(nbaFrom, transition.getAction(), nbaTo);
+
+        i++;
       }
     }
 
@@ -123,7 +124,7 @@ private NBA getCanonicalNBA() {
         builder.addAcceptingState(state);
       }
     } else {
-      for (String acceptingState : acceptingSets.get(0)) {
+      for (String acceptingState : acceptingSets.stream().findFirst().get()) {
         builder.addAcceptingState(acceptingState);
       }
     }
@@ -143,23 +144,23 @@ public static GNBA fromJson(String json) {
     return GSON.fromJson(json, GNBA.class);
   }
 
-  public List<String> getStates() {
+  public Set<String> getStates() {
     return states;
   }
 
-  public List<String> getInitialStates() {
+  public Set<String> getInitialStates() {
     return initialStates;
   }
 
-  public List<String> getAlphabet() {
+  public Set<String> getAlphabet() {
     return alphabet;
   }
 
-  public List<List<String>> getAcceptingSets() {
+  public Set<Set<String>> getAcceptingSets() {
     return acceptingSets;
   }
 
-  public List<NBATransition> getTransitions() {
+  public Set<NBATransition> getTransitions() {
     return transitions;
   }
 }
diff --git a/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBABuilder.java b/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBABuilder.java
index 3eebd52..76ab9d9 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBABuilder.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/automaton/GNBABuilder.java
@@ -1,23 +1,22 @@
 package me.paultristanwagner.modelchecking.automaton;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.HashSet;
 import java.util.Set;
 
 public class GNBABuilder {
 
-  private final List<String> states;
-  private final List<String> alphabet;
-  private final List<String> initialStates;
-  private final List<List<String>> acceptingSets;
-  private final List<NBATransition> transitions;
+  private final Set<String> states;
+  private final Set<String> alphabet;
+  private final Set<String> initialStates;
+  private final Set<Set<String>> acceptingSets;
+  private final Set<NBATransition> transitions;
 
   public GNBABuilder() {
-    this.states = new ArrayList<>();
-    this.alphabet = new ArrayList<>();
-    this.initialStates = new ArrayList<>();
-    this.acceptingSets = new ArrayList<>();
-    this.transitions = new ArrayList<>();
+    this.states = new HashSet<>();
+    this.alphabet = new HashSet<>();
+    this.initialStates = new HashSet<>();
+    this.acceptingSets = new HashSet<>();
+    this.transitions = new HashSet<>();
   }
 
   public GNBABuilder addStates(String... states) {
@@ -33,7 +32,7 @@ public GNBABuilder addState(String state) {
     return this;
   }
 
-  public GNBABuilder setAlphabet(List<String> alphabet) {
+  public GNBABuilder setAlphabet(Set<String> alphabet) {
     this.alphabet.clear();
     this.alphabet.addAll(alphabet);
     return this;
@@ -44,13 +43,8 @@ public GNBABuilder addInitialState(String initialState) {
     return this;
   }
 
-  public GNBABuilder addAcceptingSet(String... acceptingSet) {
-    this.acceptingSets.add(List.of(acceptingSet));
-    return this;
-  }
-
   public GNBABuilder addAcceptingSet(Set<String> acceptingSet) {
-    this.acceptingSets.add(new ArrayList<>(acceptingSet));
+    this.acceptingSets.add(new HashSet<>(acceptingSet));
     return this;
   }
 
diff --git a/src/main/java/me/paultristanwagner/modelchecking/automaton/NBA.java b/src/main/java/me/paultristanwagner/modelchecking/automaton/NBA.java
index 992f6cf..c41b514 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/automaton/NBA.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/automaton/NBA.java
@@ -19,18 +19,18 @@ public class NBA {
             .create();
   }
 
-  private final List<String> states;
-  private final List<String> alphabet;
-  private final List<String> initialStates;
-  private final List<String> acceptingStates;
-  private final List<NBATransition> transitions;
+  private final Set<String> states;
+  private final Set<String> alphabet;
+  private final Set<String> initialStates;
+  private final Set<String> acceptingStates;
+  private final Set<NBATransition> transitions;
 
   public NBA(
-      List<String> states,
-      List<String> alphabet,
-      List<String> initialStates,
-      List<String> acceptingStates,
-      List<NBATransition> transitions) {
+      Set<String> states,
+      Set<String> alphabet,
+      Set<String> initialStates,
+      Set<String> acceptingStates,
+      Set<NBATransition> transitions) {
     this.states = states;
     this.alphabet = alphabet;
     this.initialStates = initialStates;
@@ -138,13 +138,13 @@ public NBAEmptinessResult checkEmptiness() {
   }
 
   public GNBA toGNBA() {
-    List<String> states = new ArrayList<>(this.states);
-    List<String> alphabet = new ArrayList<>(this.alphabet);
-    List<String> initialStates = new ArrayList<>(this.initialStates);
-    List<NBATransition> transitions = new ArrayList<>(this.transitions);
+    Set<String> states = new HashSet<>(this.states);
+    Set<String> alphabet = new HashSet<>(this.alphabet);
+    Set<String> initialStates = new HashSet<>(this.initialStates);
+    Set<NBATransition> transitions = new HashSet<>(this.transitions);
 
-    List<List<String>> acceptingSets = new ArrayList<>();
-    acceptingSets.add(new ArrayList<>(this.acceptingStates));
+    Set<Set<String>> acceptingSets = new HashSet<>();
+    acceptingSets.add(new HashSet<>(this.acceptingStates));
 
     return new GNBA(states, alphabet, initialStates, acceptingSets, transitions);
   }
@@ -209,23 +209,23 @@ public static NBA fromJson(String json) {
     return GSON.fromJson(json, NBA.class);
   }
 
-  public List<String> getStates() {
+  public Set<String> getStates() {
     return states;
   }
 
-  public List<String> getAlphabet() {
+  public Set<String> getAlphabet() {
     return alphabet;
   }
 
-  public List<String> getInitialStates() {
+  public Set<String> getInitialStates() {
     return initialStates;
   }
 
-  public List<String> getAcceptingStates() {
+  public Set<String> getAcceptingStates() {
     return acceptingStates;
   }
 
-  public List<NBATransition> getTransitions() {
+  public Set<NBATransition> getTransitions() {
     return transitions;
   }
 }
diff --git a/src/main/java/me/paultristanwagner/modelchecking/automaton/NBABuilder.java b/src/main/java/me/paultristanwagner/modelchecking/automaton/NBABuilder.java
index 34527ce..640d9d4 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/automaton/NBABuilder.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/automaton/NBABuilder.java
@@ -1,22 +1,22 @@
 package me.paultristanwagner.modelchecking.automaton;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
 
 public class NBABuilder {
 
-  private final List<String> states;
-  private final List<String> alphabet;
-  private final List<String> initialStates;
-  private final List<String> acceptingStates;
-  private final List<NBATransition> transitions;
+  private final Set<String> states;
+  private final Set<String> alphabet;
+  private final Set<String> initialStates;
+  private final Set<String> acceptingStates;
+  private final Set<NBATransition> transitions;
 
   public NBABuilder() {
-    this.states = new ArrayList<>();
-    this.alphabet = new ArrayList<>();
-    this.initialStates = new ArrayList<>();
-    this.acceptingStates = new ArrayList<>();
-    this.transitions = new ArrayList<>();
+    this.states = new HashSet<>();
+    this.alphabet = new HashSet<>();
+    this.initialStates = new HashSet<>();
+    this.acceptingStates = new HashSet<>();
+    this.transitions = new HashSet<>();
   }
 
   public NBABuilder addStates(String... states) {
@@ -32,7 +32,7 @@ public NBABuilder addState(String state) {
     return this;
   }
 
-  public NBABuilder setAlphabet(List<String> alphabet) {
+  public NBABuilder setAlphabet(Set<String> alphabet) {
     this.alphabet.clear();
     this.alphabet.addAll(alphabet);
     return this;
diff --git a/src/main/java/me/paultristanwagner/modelchecking/ltl/BasicLTLModelChecker.java b/src/main/java/me/paultristanwagner/modelchecking/ltl/BasicLTLModelChecker.java
index b19d61c..5df762b 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/ltl/BasicLTLModelChecker.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/ltl/BasicLTLModelChecker.java
@@ -198,8 +198,7 @@ public Set<LTLFormula> reduceClosure(Set<LTLFormula> closure) {
     return reduced;
   }
 
-  private Set<B> computeElementarySets(
-      Set<String> atomicPropositions, Set<LTLFormula> closure) {
+  private Set<B> computeElementarySets(Set<String> atomicPropositions, Set<LTLFormula> closure) {
     Set<B> elementarySets = new HashSet<>();
 
     // todo: figure out what to do with this
@@ -224,14 +223,14 @@ private Set<B> computeElementarySets(
 
     int n = reduced.size();
     int m = 1 << n;
-    while(m > 0) {
+    while (m > 0) {
       m--;
 
       Set<LTLFormula> assumed = new HashSet<>();
 
       int i = 0;
       for (LTLFormula f : reduced) {
-        if((m & (1 << i)) != 0) {
+        if ((m & (1 << i)) != 0) {
           assumed.add(f);
         }
         i++;
diff --git a/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystem.java b/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystem.java
index 0b12b78..cb04296 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystem.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystem.java
@@ -24,18 +24,18 @@ public class TransitionSystem {
             .create();
   }
 
-  private final List<String> states;
-  private final List<TSTransition> transitions;
-  private final List<String> initialStates;
-  private final List<String> atomicPropositions;
-  private final Map<String, List<String>> labelingFunction;
+  private final Set<String> states;
+  private final Set<TSTransition> transitions;
+  private final Set<String> initialStates;
+  private final Set<String> atomicPropositions;
+  private final Map<String, Set<String>> labelingFunction;
 
   public TransitionSystem(
-      List<String> states,
-      List<TSTransition> transitions,
-      List<String> initialStates,
-      List<String> atomicPropositions,
-      Map<String, List<String>> labelingFunction) {
+      Set<String> states,
+      Set<TSTransition> transitions,
+      Set<String> initialStates,
+      Set<String> atomicPropositions,
+      Map<String, Set<String>> labelingFunction) {
     this.states = states;
     this.transitions = transitions;
     this.initialStates = initialStates;
@@ -43,7 +43,7 @@ public TransitionSystem(
     this.labelingFunction = labelingFunction;
 
     for (String state : states) {
-      labelingFunction.putIfAbsent(state, List.of());
+      labelingFunction.putIfAbsent(state, Set.of());
     }
   }
 
@@ -57,14 +57,14 @@ public void verifyNoNullLabels() {
   }
 
   public TransitionSystem copy() {
-    List<String> states = new ArrayList<>(this.states);
-    List<TSTransition> transitions = new ArrayList<>(this.transitions);
-    List<String> initialStates = new ArrayList<>(this.initialStates);
-    List<String> atomicPropositions = new ArrayList<>(this.atomicPropositions);
+    Set<String> states = new HashSet<>(this.states);
+    Set<TSTransition> transitions = new HashSet<>(this.transitions);
+    Set<String> initialStates = new HashSet<>(this.initialStates);
+    Set<String> atomicPropositions = new HashSet<>(this.atomicPropositions);
 
-    Map<String, List<String>> labelingFunction = new HashMap<>();
+    Map<String, Set<String>> labelingFunction = new HashMap<>();
     this.labelingFunction.forEach(
-        (state, labels) -> labelingFunction.put(state, new ArrayList<>(labels)));
+        (state, labels) -> labelingFunction.put(state, new HashSet<>(labels)));
 
     return new TransitionSystem(
         states, transitions, initialStates, atomicPropositions, labelingFunction);
@@ -79,7 +79,7 @@ public TransitionSystem reachableSynchronousProduct(NBA nba) {
 
     Queue<SimpleEntry<String, String>> queue = new ArrayDeque<>();
     for (String initialState : initialStates) {
-      List<String> label = labelingFunction.get(initialState);
+      Set<String> label = labelingFunction.get(initialState);
 
       for (NBATransition nbaTransition : nba.getTransitions()) {
         String q0 = nbaTransition.getFrom();
@@ -122,7 +122,7 @@ public TransitionSystem reachableSynchronousProduct(NBA nba) {
       List<String> sSuccessors = getSuccessors(s);
 
       for (String sSuccessor : sSuccessors) {
-        List<String> sSuccessorLabel = labelingFunction.get(sSuccessor);
+        Set<String> sSuccessorLabel = labelingFunction.get(sSuccessor);
         String sSuccessorLabelString = sSuccessorLabel.toString();
         Set<String> qSuccessors = nba.getSuccessors(q, sSuccessorLabelString);
         for (String qSuccessor : qSuccessors) {
@@ -201,7 +201,7 @@ public TSPersistenceResult checkPersistence(Set<String> persistentStates) {
           pi.push(s1);
         } else {
           pi.pop();
-          List<String> labels = labelingFunction.get(s);
+          Set<String> labels = labelingFunction.get(s);
 
           boolean notPersistentState = labels.stream().noneMatch(persistentStates::contains);
 
@@ -244,11 +244,11 @@ public String toString() {
     return toJson();
   }
 
-  public List<String> getStates() {
+  public Set<String> getStates() {
     return states;
   }
 
-  public List<String> getInitialStates() {
+  public Set<String> getInitialStates() {
     return initialStates;
   }
 
@@ -260,7 +260,7 @@ public List<String> getSuccessors(String state) {
         .toList();
   }
 
-  public List<String> getAtomicPropositions() {
+  public Set<String> getAtomicPropositions() {
     return atomicPropositions;
   }
 
@@ -268,7 +268,7 @@ public void addLabel(String state, String atomicProposition) {
     labelingFunction.get(state).add(atomicProposition);
   }
 
-  public List<String> getLabel(String state) {
+  public Set<String> getLabel(String state) {
     return labelingFunction.get(state);
   }
 
diff --git a/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystemBuilder.java b/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystemBuilder.java
index 9663586..85b5399 100644
--- a/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystemBuilder.java
+++ b/src/main/java/me/paultristanwagner/modelchecking/ts/TransitionSystemBuilder.java
@@ -4,17 +4,17 @@
 
 public class TransitionSystemBuilder {
 
-  private final List<String> states;
-  private final List<TSTransition> transitions;
-  private final List<String> initialStates;
-  private final List<String> atomicPropositions;
-  private final Map<String, List<String>> labelingFunction;
+  private final Set<String> states;
+  private final Set<TSTransition> transitions;
+  private final Set<String> initialStates;
+  private final Set<String> atomicPropositions;
+  private final Map<String, Set<String>> labelingFunction;
 
   public TransitionSystemBuilder() {
-    this.states = new ArrayList<>();
-    this.transitions = new ArrayList<>();
-    this.initialStates = new ArrayList<>();
-    this.atomicPropositions = new ArrayList<>();
+    this.states = new HashSet<>();
+    this.transitions = new HashSet<>();
+    this.initialStates = new HashSet<>();
+    this.atomicPropositions = new HashSet<>();
     this.labelingFunction = new HashMap<>();
   }
 
@@ -62,14 +62,14 @@ public TransitionSystemBuilder addAtomicProposition(String atomicProposition) {
   }
 
   public TransitionSystemBuilder addLabel(String state, String atomicProposition) {
-    List<String> labels = labelingFunction.computeIfAbsent(state, k -> new ArrayList<>());
+    Set<String> labels = labelingFunction.computeIfAbsent(state, k -> new HashSet<>());
     labels.add(atomicProposition);
 
     return this;
   }
 
   public TransitionSystemBuilder addLabels(String state, String... atomicPropositions) {
-    List<String> labels = labelingFunction.computeIfAbsent(state, k -> new ArrayList<>());
+    Set<String> labels = labelingFunction.computeIfAbsent(state, k -> new HashSet<>());
     labels.addAll(Arrays.asList(atomicPropositions));
 
     return this;
@@ -80,7 +80,7 @@ public TransitionSystem build() {
         states, transitions, initialStates, atomicPropositions, labelingFunction);
   }
 
-  public List<String> getInitialStates() {
+  public Set<String> getInitialStates() {
     return initialStates;
   }
 }