Update 'README.md'

README.md

@@ -40,6 +40,7 @@ ___
 - [A divided Ukraine](https://www.cnn.com/interactive/2014/02/world/ukraine-divided/)
 - [HIKIKOMORI a deafening silence - documentary ](https://www.youtube.com/watch?v=zzF83e_L100)
 - [Xylitol](https://en.wikipedia.org/wiki/Xylitol#cite_note-Riley-etal-2015-4)
+- [Universally unique identifier](https://en.wikipedia.org/wiki/Universally_unique_identifier)
 
  
 ## [Mathematics and Theoretical Computer Science](mathematics.md)