Computer Systems Research Group
The University of California at Berkeley's Computer Systems Research Group (CSRG is the usual short form of the name) is is the group that was responsible for CSRG BSD. (Not to mention biff, vi, and of course sendmail.)
Kirk has released CD sets containing as much of the work of the CSRG as possible. You can download ISO's of them here.
- Twenty Years of Berkeley Unix: From AT&T-Owned to Freely Redistributable - An excellent overview of the history of the CSRG, as told by Marshall Kirk McKusick
- The Daemon, the GNU and the Penguin: Chapter 7 - BSD and the CSRG