S. Ji, G. Li, C. Li, and J. Feng. WWW '09: Proceedings of the 18th international conference on World wide web, page 371--380. New York, NY, USA, ACM, (2009)
M. Pa\csca. CIKM '07: Proceedings of the sixteenth ACM conference on Conference on information and knowledge management, page 683--690. New York, NY, USA, ACM, (2007)