C. Buckley, and E. Voorhees. Proceedings of the 27th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval (SIGIR 2004), page 25--32. Sheffield, United Kingdom, ACM, (July 2004)
J. Najjar, S. Ternier, and E. Duval. Proceedings of the ED-MEDIA 2004 World Conference on Educational Multimedia, Hypermedia and Telecommunications, (June 2004)