diff --git a/README.md b/README.md
index 75c84d3..57eb32f 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,21 @@ C++ tips tricks and idioms
 
 ~~~
 private constructor
+
 singleton pattern
+
 swap trick
+
+
+prevent class inheritance
+http://stackoverflow.com/questions/2184133/prevent-class-inheritance-in-c
+
+virtual destructor
+
+virtual inheritance
+http://stackoverflow.com/questions/21558/in-c-what-is-a-virtual-base-class
+
+virtual function
+http://stackoverflow.com/questions/2391679/why-do-we-need-virtual-functions-in-c
+
 ~~~