J. Mueller, S. Doerfel, M. Becker, A. Hotho, and G. Stumme. Proceedings of the Fifth ACM RecSys Workshop on Recommender Systems and the Social Web co-located with the 7th ACM Conference on Recommender Systems (RecSys 2013), CEUR-WS, (2013)
H. Zhang, M. Korayem, E. You, and D. Crandall. Proceedings of the Fifth ACM International Conference on Web Search and Data Mining, page 33--42. New York, NY, USA, ACM, (2012)