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)
T. Richter, P. Grube, and D. Zutin. 2012 IEEE International Symposium on Multimedia ISM 2012, page 451 - 456. Irvine, California, USA, IEEE, IEEE, (December 2012)