add link to README, including links and notes in Related Works

cryptography/README.md

@@ -1,2 +1,10 @@
 * [A Method for Obtaining Digital Signatures and Public-Key Cryptosystems](http://people.csail.mit.edu/rivest/Rsapaper.pdf)
 * [Twenty Years of Attacks on the RSA Cryptosystem](https://crypto.stanford.edu/~dabo/papers/RSA-survey.pdf)
+* ["Communication Theory of Secrecy Systems"](communication-theory-of-secrecy-systems.pdf)
+
+## Related Works
+### ["A Mathematical Theory of Cryptography" (1945) - Shannon](http://www.cs.bell-labs.com/who/dmr/pdfs/shannoncryptshrt.pdf)
+The original classified memo for Bell Labs that was republished in 1949 as ["Communication Theory of Secrecy Systems"](communication-theory-of-secrecy-systems.pdf).
+
+### ["A Mathematical Theory of Communication" (1945) - Shannon](../information_theory/a-mathematical-theory-of-communication-1948.pdf)
+Shannon said that his wartime insights into communication theory and cryptography developed simultaneously and that "they were so close together you couldn’t separate them". ["Communication Theory of Secrecy Systems"](communication-theory-of-secrecy-systems.pdf) incorporates many concepts and formulations that also appeared in his 1948 paper.