X. Song, Y. Chi, K. Hino, and B. Tseng. WWW '07: Proceedings of the 16th international conference on World Wide Web, page 191--200. New York, NY, USA, ACM Press, (2007)
B. Piwowarski, and H. Zaragoza. CIKM '07: Proceedings of the sixteenth ACM conference on Conference on information and knowledge management, page 175--182. New York, NY, USA, ACM, (2007)
D. Agarwal, B. Chen, and P. Elango. WWW '09: Proceedings of the 18th international conference on World wide web, page 21--30. New York, NY, USA, ACM, (2009)
M. Cha, A. Mislove, and K. Gummadi. WWW '09: Proceedings of the 18th international conference on World wide web, page 721--730. New York, NY, USA, ACM, (2009)