S. Doerfel, R. Jäschke, A. Hotho, and G. Stumme. Proceedings of the 4th ACM RecSys workshop on Recommender systems and the social web, page 9--16. New York, NY, USA, ACM, (2012)
C. Cattuto, D. Benz, A. Hotho, and G. Stumme. The Semantic Web - ISWC 2008, volume 5318 of Lecture Notes in Computer Science, page 615--631. Springer Berlin / Heidelberg, (2008)