D. Liu, X. Hua, L. Yang, M. Wang, and H. Zhang. Proceedings of the 18th international conference on World wide web, page 351--360. New York, NY, USA, ACM, (2009)
C. Cattuto, D. Benz, A. Hotho, and G. Stumme. The Semantic Web - ISWC 2008, volume 5318 of Lecture Notes in Computer Science, Springer Berlin / Heidelberg, (2008)
S. Bao, G. Xue, X. Wu, Y. Yu, B. Fei, and Z. Su. WWW '07: Proceedings of the 16th international conference on World Wide Web, New York, NY, USA, ACM Press, (2007)