APA Style

Thermos, P., Takanen, A. (2007). Securing VoIP networks: threats, vulnerabilities, and countermeasures (--). New Jersey: Addison-Wesley.

MLA Style

Thermos, Peter., Takanen, Ari. "Securing VoIP networks: threats, vulnerabilities, and countermeasures". -- New Jersey: Addison-Wesley, 2007. Text.