X. Wu, L. Zhang, and Y. Yu. WWW '06: Proceedings of the 15th international conference on World Wide Web, page 417-426. New York, NY, USA, ACM Press, (2006)
C. Marshall, and F. Shipman. HYPERTEXT '03: Proceedings of the fourteenth ACM conference on Hypertext and hypermedia, page 57-66. New York, NY, USA, ACM Press, (2003)