Update 'README.md'

README.md

@@ -35,6 +35,7 @@ ___
 - [Post-quantum cryptography](https://www.nature.com/articles/nature23461)
 - https://bartoszmilewski.com/2015/03/13/function-types/
 - [Banach Tarski Paradox](https://en.wikipedia.org/wiki/Banach%E2%80%93Tarski_paradox)
+- [Courcelle's Theorem](https://en.wikipedia.org/wiki/Courcelle%27s_theorem)
 
 
 ## [Mathematics and Theoretical Computer Science](mathematics.md)