Dimitris Geneiatakis Tasos Dagiuklas Georgios Kambourakis Costas Lambrinoudakis Stefanos Gritzalis Sven Ehlert Dorgham Sisalem Survey of security vulnerabilities in session initiation protocol. 68-81 2006 8 IEEE Communications Surveys and Tutorials 1-4 http://dx.doi.org/10.1109/COMST.2006.253270 db/journals/comsur/comsur8.html#GeneiatakisDKLGES06