1. Wikipedia: Lawful Interception.
http://en.wikipedia.org/wiki/Lawful_interception
2. Council of Europe: Convention on Cybercrime, 2001, ETS No. 185.
http://conventions.coe.int/Treaty/EN/Treaties/Html/185.htm
3. Council of Europe: Convention on Cybercrime Treaty Signature Status (2010).
http://conventions.coe.int/Treaty/Commun/ChercheSig.asp?NT=185&CM=8&DF=28/10/2010&CL=ENG
4. European Telecommunications Standards Institute: About ETSI.
http://www.etsi.org/about
5. Electronic Frontier Foundation: CALEA F.A.Q.
https://www.eff.org/pages/calea-faq