diff --git a/src/org/ntlab/deltaViewer/CollaborationViewer.java b/src/org/ntlab/deltaViewer/CollaborationViewer.java
index 2cfe039..d23bfc6 100644
--- a/src/org/ntlab/deltaViewer/CollaborationViewer.java
+++ b/src/org/ntlab/deltaViewer/CollaborationViewer.java
@@ -541,7 +541,7 @@
 			}
 			
 			
-			if (srcClassName != null && fieldName != null && !edgeMap.containsKey(srcClassName + "." + fieldName)) {
+			if (srcClassName != null && fieldName != null && !edgeMap.containsKey(curAliasObjId + "." + fieldName)) {
 				// Judge AliasList contains relatedPoint. (If contains not to create edge.)
 				if (rpIndex < relatedPoints.size() - 1) {
 					TracePoint rp = relatedPoints.get(rpIndex);
@@ -569,7 +569,9 @@
 						Point2D absPtSrcCell = getAbsolutePointforCell((mxICell)srcCell);
 						Point2D absPtDstCell = getAbsolutePointforCell((mxICell)dstCell);
 						setEdgePoint((mxICell)edge, absPtSrcCell, absPtDstCell);
-						edgeMap.put(srcClassName + "." + fieldName, new Edge(fieldName, TypeName.Reference, edge));
+						edgeMap.put(curAliasObjId + "." + fieldName, new Edge(fieldName, TypeName.Reference, edge));
+					} else {
+						edgeMap.put(curAliasObjId + "." + fieldName, new Edge(fieldName, TypeName.PreReference, curAliasObjId, nextAliasObjId));
 					}
 				} finally {
 					mxgraph.getModel().endUpdate();