1. Rosenberg, J., et al.: Session Initiation Protocol (SIP), RFC 3261 (June 2002)
2. El Sawda, S., Urien, P.: SIP security attacks and solutions: A state-of-the-art review. In: Proc. of IEEE International Conference on Information and Communication Technologies: From Theory to Applications (ICTTA 2006), April 2006, vol. 2, pp. 3187–3191 (2006)
3. Rosenberg, J., Jennings, C.: The Session Initiation Protocol (SIP) and Spam, RFC 5039, Network Working Group (January 2008)
4. Tschofenig, H., Wing, D., Schulzrinne, H., Froment, T., Dawirs, G.: A document format for expressing authorization policies to tackle spam and unwanted communication for Internet Telephony (draft-tschofenig-sipping-spit-policy-02.txt)
5. Lennox, J., Wu, X., Schulzrinne, H.: Call Processing Language(CPL): A Language for User Control of Internet Telephony Services. RFC 3880, Columbia University (October 2004)