C. Brooks, and N. Montanez. WWW '06: Proceedings of the 15th international conference on World Wide Web, page 625-632. New York, NY, USA, ACM Press, (2006)
R. Kumar, J. Novak, and A. Tomkins. KDD '06: Proceedings of the 12th ACM SIGKDD international conference on Knowledge discovery and data mining, page 611--617. New York, NY, USA, ACM Press, (2006)
P. Kolari, A. Java, T. Finin, T. Oates, and A. Joshi. proceedings of the 21st national conference on Artificial intelligence - Volume 2, page 1351--1356. AAAI Press, (2006)