F. Suchanek, G. Kasneci, und G. Weikum. Proceedings of the 16th international conference on World Wide Web, Seite 697--706. New York, NY, USA, ACM, (2007)
F. Baader, B. Ganter, B. Sertkaya, und U. Sattler. Proceedings of the 20th international joint conference on Artifical intelligence, Seite 230--235. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (2007)