T. Hofmann. Proceedings of the 22nd Annual International ACM SIGIR Conference on Research and Development in Information Retrieval (SIGIR '99), August 15-19, 1999, Berkeley, CA, USA, Seite 50--57. ACM Press, New York, NY, USA, (1999)
L. Cai, und T. Hofmann. Proceedings of the 26th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval (SIGIR '03), July 28 - August 1, 2003, Toronto, Canada, Seite 182--189. ACM Press, New York, NY, USA, (2003)