T. Joachims. Proceedings of the Eighth ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, page 133--142. New York, NY, USA, ACM, (2002)
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proceedings of the 3rd European Semantic Web Conference, volume 4011 of LNCS, page 411-426. Budva, Montenegro, Springer, (June 2006)