How Linux Works: What Every Superuser Should Know
Brian Ward
Network Security Through Data Analysis: Building Situational ...
Michael Collins
Hacking VoIP: Protocols, Attacks, and Countermeasures
Himanshu Dwivedi
UNIX and Linux System Administration Handbook 4th edition
Evi Nemeth & Garth Snyder & Trent R. Hein & Ben Whaley
Java: The Complete Reference, Ninth Edition
Herbert Schildt