Lion, John Lion's Commentary on UNIX, 6th Ed. With Source Code. ITP Media Group, 1996. ISBN 1573980137
Raymond, Eric S. The New Hacker's Dictionary, 3rd edition. MIT Press, 1996. ISBN 0-262-68092-0. Also known as the Jargon File
Salus, Peter H. A quarter century of UNIX. Addison-Wesley Publishing Company, Inc., 1994. ISBN 0-201-54777-5
Simon Garfinkel, Daniel Weise, Steven Strassmann. The UNIX-HATERS Handbook. IDG Books Worldwide, Inc., 1994. ISBN 1-56884-203-1. Out of print, but available online.
Don Libes, Sandy Ressler Life with UNIX -- special edition. Prentice-Hall, Inc., 1989. ISBN 0-13-536657-7
The BSD family tree. http://www.FreeBSD.org/cgi/cvsweb.cgi/src/share/misc/bsd-family-tree or /usr/share/misc/bsd-family-tree on a FreeBSD machine.
Networked Computer Science Technical Reports Library. http://www.ncstrl.org/
Old BSD releases from the Computer Systems Research group (CSRG). http://www.mckusick.com/csrg/: The 4CD set covers all BSD versions from 1BSD to 4.4BSD and 4.4BSD-Lite2 (but not 2.11BSD, unfortunately). The last disk also holds the final sources plus the SCCS files.