Where can I find the source code for BSD or GNU shell commands like ps, cd, ls, etc. that are built for Mac or Unix? - Quora
NetBSD - Wikiwand
History of Unix - Wikiwand
The number of files and LOC of BSD UNIX | Download Table
Unix Systems Administration 1Y. K. Chang UNIX History : Bell Lab joined with GEC and Project MAC of MIT to develop Multics: multi-user and data-sharing. - ppt download
FreeBSD
CFT: OSCON 2012: Bring Back BSD
A simplified diagram of Unix variants and releases related through... | Download Scientific Diagram