Update 'backlog.md'

backlog.md

@@ -62,6 +62,7 @@
 - [AS WE MAY THINK by VANNEVAR BUSH](http://web.mit.edu/STS.035/www/PDFs/think.pdf)
 - [A beginner's guide to forcing](https://arxiv.org/abs/0712.1320)
 - [Probability Analysis of UUID dupicates](https://en.wikipedia.org/wiki/Universally_unique_identifier#Random_UUID_probability_of_duplicates)
+- [Shannon's Source Coding Theorem](https://en.wikipedia.org/wiki/Shannon%27s_source_coding_theorem)