Asterisk: The Definitive Guide
Jim Van Meggelen & Russell Bryant & Leif Madsen
Linux Advanced Routing and Traffic Control HOWTO
Gregory Maxwell & Remco Mook & Martijn Oosterhout & Paul Schroeder & Jasper Spaans & Bert Hubert
C++ Crash Course
Josh Lospinoso
Pluggable Authentication Modules
Kenneth Geisshirt