Update 'backlog.md'

backlog.md

@@ -58,6 +58,7 @@
 - [Galois Connection](https://en.wikipedia.org/wiki/Galois_connection)
 - [Groebner Basis](https://en.wikipedia.org/wiki/Gr%C3%B6bner_basis)
 - [Nim](https://en.wikipedia.org/wiki/Nim)
+- [AS WE MAY THINK by VANNEVAR BUSH](http://web.mit.edu/STS.035/www/PDFs/think.pdf)
 
 ## Reference Book Backlog
 - Bartlett's Familiar Quotations