D. Ramage, P. Heymann, C. Manning, and H. Garcia-Molina. WSDM '09: Proceedings of the Second ACM International Conference on Web Search and Data Mining, page 54--63. New York, NY, USA, ACM, (2009)
P. Cimiano, A. Hotho, and S. Staab. ECAI 2004 Proceedings of the 16th European Conference on Artificial Intelligence, 22 - 27 August, Valencia, Spain, page 435-439. IOS Press, (2004)
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)