P. Brandtzæg, A. Følstad, M. Obrist, D. Geerts, und R. Berg. UCMedia, Volume 40 von Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, Seite 50-57. Springer, (2009)
D. Geerts. UCMedia, Volume 40 von Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, Seite 357-360. Springer, (2009)