diff --git a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
index 2c2ca6b2..81c6da3a 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
@@ -315,7 +315,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		List<Set<UnifyPair>> nextSetasList =new ArrayList<>(nextSet);
 		try {
 		//List<Set<UnifyPair>> 
-		nextSetasList = oup.sortedCopy(nextSet);//new ArrayList<>(nextSet);
+			//nextSetasList = oup.sortedCopy(nextSet);//new ArrayList<>(nextSet);
 		}
 		catch (java.lang.IllegalArgumentException e) {
 			System.out.print("");
@@ -815,6 +815,16 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 				//List<UnifyType> freshTphs = new ArrayList<>(); PL 18-02-06 in die For-Schleife verschoben
 				for (UnifyType tq : thetaQs) {
 					Set<UnifyType> smaller = fc.smaller(unifier.apply(tq)); 
+					//eingefuegt PL 2018-03-29 Anfang ? ext. theta hinzufuegen
+					Set<UnifyType> smaller_ext = smaller.stream()
+							.map(x -> {
+								BinaryOperator<HashMap<PlaceholderType,PlaceholderType>> combiner = (aa,b) -> { aa.putAll(b); return aa;};
+								HashMap<PlaceholderType,PlaceholderType> hm = x.getInvolvedPlaceholderTypes().stream()
+										.reduce(new HashMap<PlaceholderType,PlaceholderType>(), 
+												(aa, b)-> { aa.put(b,PlaceholderType.freshPlaceholder()); return aa; }, combiner);
+								return new ExtendsType (x.accept(new freshPlaceholder(), hm));}).collect(Collectors.toCollection(HashSet::new));
+					smaller.addAll(smaller_ext);
+					//eingefuegt PL 2018-03-29 Ende ? ext. theta hinzufuegen
 					for(UnifyType theta : smaller) {
 						List<UnifyType> freshTphs = new ArrayList<>();
 						Set<UnifyPair> resultPrime = new HashSet<>();
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/Unifier.java b/src/de/dhbwstuttgart/typeinference/unify/model/Unifier.java
index 7b32864d..1ee05264 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/Unifier.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/Unifier.java
@@ -63,7 +63,12 @@ public class Unifier implements Function<UnifyType, UnifyType>, Iterable<Entry<P
 	 * @return A new pair where the left and right-hand side are applied
 	 */
 	public UnifyPair apply(UnifyPair p) {
-		return new UnifyPair(this.apply(p.getLhsType()), this.apply(p.getRhsType()), p.getPairOp(), this, p);
+		UnifyType newLhs = this.apply(p.getLhsType());
+		UnifyType newRhs = this.apply(p.getRhsType());
+		if (!(p.getLhsType().equals(newLhs)) || !(p.getRhsType().equals(newRhs))) {//Die Anwedung von this hat was veraendert PL 2018-04-01
+			return new UnifyPair(newLhs, newRhs, p.getPairOp(), this, p);
+		}
+		return new UnifyPair(newLhs, newRhs, p.getPairOp(), p.getSubstitution(), p.getBasePair());
 	}
 	
 	/**
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
index 098ff946..173b5f8c 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
@@ -26,7 +26,7 @@ public class UnifyPair {
 	 */
 	private PairOperator pairOp;
 	
-	/**
+	/** wieder loesecn wird nicht mehr benoetigt PL 2018-03-31
      * variance shows the variance of the pair
      * -1: contravariant
      * 1 covariant
@@ -38,10 +38,10 @@ public class UnifyPair {
     private boolean undefinedPair = false;
     
     /**
-     * Unifier that generated this pair
+     * Unifier/substitute that generated this pair
      * PL 2018-03-15
      */
-    private Unifier unifier;
+    private Unifier substitution;
     
     /**
      * Base on which the the unifier is applied
@@ -70,7 +70,7 @@ public class UnifyPair {
 		this.lhs = lhs;
 		this.rhs = rhs;
 		pairOp = op;
-		unifier = uni;
+		substitution = uni;
 		basePair = base;
 		this.variance = variance;
 		
@@ -111,7 +111,13 @@ public class UnifyPair {
 	public void setUndefinedPair() {
 		undefinedPair = true;
 	}
-
+	public Unifier getSubstitution() {
+		return substitution;
+	}
+	
+	public UnifyPair getBasePair() {
+		return basePair;
+	}
 	public boolean isUndefinedPair() {
 		return undefinedPair;
 	}