S. Berger, A. Vensmer, and S. Kiesel. Proceedings of the The Seventh International Conference on Systems and Networks Communications (ICSNC 2012), page 118 -- 123. Lisbon, Portugal, (November 2012)
D. Boehringer, B. Burr, S. Jeschke, and T. Richter. Proceedings of the 2009 World Conference on Educational Multimedia, Hypermedia \\\& Telecommunications, page 1124-1129. Honolulu, HI, USA, AACE, (June 2009)