diff --git a/README.md b/README.md
index 4c19c76..ed61a7f 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,7 @@ private constructor
 swap trick
 
 move semantics
+https://stackoverflow.com/questions/3106110/what-are-move-semantics
 
 prevent class inheritance
 http://stackoverflow.com/questions/2184133/prevent-class-inheritance-in-c