J. Ahn, P. Brusilovsky, J. Grady, D. He, and S. Syn. WWW '07: Proceedings of the 16th international conference on World Wide Web, page 11--20. New York, NY, USA, ACM Press, (2007)
A. Das, M. Datar, A. Garg, and S. Rajaram. WWW '07: Proceedings of the 16th international conference on World Wide Web, page 271--280. New York, NY, USA, ACM Press, (2007)