B. Sarwar, G. Karypis, J. Konstan, and J. Reidl. Proceedings of the 10th International Conference on World Wide Web, page 285--295. New York, NY, USA, ACM, (2001)
J. Vig, S. Sen, and J. Riedl. IUI '09: Proceedings of the 13th international conference on Intelligent user interfaces, page 47--56. New York, NY, USA, ACM, (2008)