diff --git a/src/org/ntlab/deltaViewer/CollaborationLayout.java b/src/org/ntlab/deltaViewer/CollaborationLayout.java
index 6b428c8..bf3aad3 100644
--- a/src/org/ntlab/deltaViewer/CollaborationLayout.java
+++ b/src/org/ntlab/deltaViewer/CollaborationLayout.java
@@ -21,6 +21,7 @@
 import org.ntlab.trace.MethodInvocation;
 import org.ntlab.trace.Reference;
 import org.ntlab.trace.Statement;
+import org.ntlab.trace.TracePoint;
 
 import com.mxgraph.model.mxICell;
 import com.mxgraph.util.mxPoint;
@@ -37,37 +38,48 @@
 		padding = 200;
 		
 		// Extract the bottom reference.
-		Statement relatedSt = objectCallGraph.getRelatedPoints().get(objectCallGraph.getRelatedPoints().size() - 1).getStatement();
+		TracePoint relatedPt = objectCallGraph.getRelatedPoints().get(objectCallGraph.getRelatedPoints().size() - 1);
+		Statement relatedSt = relatedPt.getStatement();
 		String bottomSrcObjId = null;
 		String bottomDstObjId = null;
-		if (relatedSt instanceof FieldUpdate) {
-			// container to component
-			bottomSrcObjId = ((FieldUpdate) relatedSt).getContainerObjId();
-			bottomDstObjId = ((FieldUpdate) relatedSt).getValueObjId();
-		} else if (relatedSt instanceof ArrayUpdate) {
-			// container to component
-			bottomSrcObjId = ((ArrayUpdate) relatedSt).getArrayObjectId();
-			bottomDstObjId = ((ArrayUpdate) relatedSt).getValueObjectId();
-		} else if (relatedSt instanceof MethodInvocation) {
-			MethodInvocation methodInvStatement = (MethodInvocation) relatedSt;
-			MethodExecution calledMethodExec = methodInvStatement.getCalledMethodExecution();
-			String methodSignature = calledMethodExec.getSignature();
-			if (calledMethodExec.isCollectionType()
-					&& (methodSignature.contains("add(") 
-							|| methodSignature.contains("set(") 
-							|| methodSignature.contains("put(") 
-							|| methodSignature.contains("push(") 
-							|| methodSignature.contains("addElement("))) {
-				// container to component
-				bottomSrcObjId = calledMethodExec.getThisObjId();
-				bottomDstObjId = calledMethodExec.getArguments().get(0).getId();
-			} else {
-				// this to another
-				bottomSrcObjId = methodInvStatement.getThisObjId();
-				bottomDstObjId = calledMethodExec.getReturnValue().getId();
+		if (relatedPt.isMethodEntry()) {
+			// this to another (parameter)
+			Alias lastAlias = aliasCollector.getAliasList().get(aliasCollector.getAliasList().size() - 1);
+			if (lastAlias.getAliasType() == Alias.AliasType.FORMAL_PARAMETER) {
+				bottomSrcObjId = relatedPt.getMethodExecution().getThisObjId();
+				bottomDstObjId = lastAlias.getObjectId();
 			}
-		} else {
-			return;
+		}
+		if (bottomSrcObjId == null || bottomDstObjId == null) {
+			if (relatedSt instanceof FieldUpdate) {
+				// container to component
+				bottomSrcObjId = ((FieldUpdate) relatedSt).getContainerObjId();
+				bottomDstObjId = ((FieldUpdate) relatedSt).getValueObjId();
+			} else if (relatedSt instanceof ArrayUpdate) {
+				// container to component
+				bottomSrcObjId = ((ArrayUpdate) relatedSt).getArrayObjectId();
+				bottomDstObjId = ((ArrayUpdate) relatedSt).getValueObjectId();
+			} else if (relatedSt instanceof MethodInvocation) {
+				MethodInvocation methodInvStatement = (MethodInvocation) relatedSt;
+				MethodExecution calledMethodExec = methodInvStatement.getCalledMethodExecution();
+				String methodSignature = calledMethodExec.getSignature();
+				if (calledMethodExec.isCollectionType()
+						&& (methodSignature.contains("add(") 
+								|| methodSignature.contains("set(") 
+								|| methodSignature.contains("put(") 
+								|| methodSignature.contains("push(") 
+								|| methodSignature.contains("addElement("))) {
+					// container to component
+					bottomSrcObjId = calledMethodExec.getThisObjId();
+					bottomDstObjId = calledMethodExec.getArguments().get(0).getId();
+				} else {
+					// this to another
+					bottomSrcObjId = methodInvStatement.getThisObjId();
+					bottomDstObjId = calledMethodExec.getReturnValue().getId();
+				}
+			} else {
+				return;
+			}
 		}
 		
 		// Extract the reference access history.