diff --git a/relation.py b/relation.py
index d9175ab..e67b8e7 100644
--- a/relation.py
+++ b/relation.py
@@ -68,7 +68,9 @@ class relation (object):
 		
 		for i in self.content:
 			for j in other.content:
-				newt.content.append(i+j)
+				n=i+j
+				if n not in newt.content:
+					newt.content.append(i+j)
 		return newt