diff --git a/501-nsm.md b/501-nsm.md
index 48b7813..1dc9694 100644
--- a/501-nsm.md
+++ b/501-nsm.md
@@ -27,6 +27,11 @@
 
 ## Module II 
 - Numerical differentiation at the tabulated points with forward, backward and central differences. 
+        - [SK Maths - Tamil - (v.v.good)](https://www.youtube.com/watch?v=S5zAWGSTCOE&list=PLA-HuD2_X05P1eK-5oa9tarbh9qaGXBE0)
+        - [Roslin George - Malayalam](https://www.youtube.com/watch?v=sRphyn1qaSM)
+        - [Infinite Math - English](https://www.youtube.com/watch?v=5zwxZ439nTA)
+
+        
 - Numerical integration with
 -  trapezoidal rule,
 - Simpson’s 1/3 rule,