T. Bogers, and A. van den Bosch. RecSys '08: Proceedings of the 2008 ACM conference on Recommender systems, page 287--290. New York, NY, USA, ACM, (2008)
A. Dattolo, F. Ferrara, and C. Tasso. Proc. of the 3rd International Conference on Human System Interaction - HSI'2010, page 548--555. IEEE Press, (May 2010)