diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/PairOperator.java b/src/de/dhbwstuttgart/typeinference/unify/model/PairOperator.java
index 7b8258bd8..fd18f6c02 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/PairOperator.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/PairOperator.java
@@ -1,22 +1,42 @@
 package de.dhbwstuttgart.typeinference.unify.model;
 
+/**
+ * Operators of pairs of the unification.
+ * @author Florian Steurer
+ */
 public enum PairOperator {
+	/**
+	 * The smaller operator (T < P) is used to express a subtyping relation between
+	 * T and P for example in the finite closure. It is necessarily true.
+	 */
 	SMALLER,
+	
+	/**
+	 * The smallerdot operator (T <. P) is used to express a subtyping relation between
+	 * of T and P in a CONSTRAINT during the unification. It is not necessarily true. 
+	 */
 	SMALLERDOT,
+	
+	/**
+	 * The smallerdot operator for arguments (T <.? P) is used to express that 
+	 * T is an element of smArg(P) (or P is an element of grArg(T)) in a CONSTRAINT 
+	 * during the unification. It is not necessarily true.
+	 */
 	SMALLERDOTWC,
+	
+	/**
+	 * The equalsdot operator (T =. P) is used to express that two types during the unification
+	 * should be equal. It is not necessarily true.
+	 */
 	EQUALSDOT;
 	
 	@Override
 	public String toString() {
 		switch (this) {
-		case SMALLER:
-			return "<";
-		case SMALLERDOT:
-			return "<.";
-		case SMALLERDOTWC:
-			return "<.?";
-		default:
-			return "=.";
+			case SMALLER: return "<";
+			case SMALLERDOT: return "<.";
+			case SMALLERDOTWC: return "<.?";
+			default: return "=."; // EQUALSDOT
 		}
-	};
+	}
 }
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