P. Klügl, M. Toepfer, F. Lemmerich, A. Hotho, and F. Puppe. Proceedings of 1st International Conference on Pattern Recognition Applications and Methods ICPRAM, page 240-248. Vilamoura, Algarve, Portugal, SciTePress, (2012)
R. Jäschke, A. Hotho, F. Mitzlaff, and G. Stumme. Recommender Systems for the Social Web, volume 32 of Intelligent Systems Reference Library, Springer, Berlin/Heidelberg, (2012)