H. Li, Y. Cao, J. Xu, Y. Hu, S. Li, and D. Meyerzon. CIKM '05: Proceedings of the 14th ACM international conference on Information and knowledge management, page 460--468. New York, NY, USA, ACM, (2005)
P. Dmitriev, N. Eiron, M. Fontoura, and E. Shekita. WWW '06: Proceedings of the 15th international conference on World Wide Web, page 811--817. New York, NY, USA, ACM Press, (2006)