J. Basilico, and T. Hofmann. Proceedings of the 27th annual international ACM SIGIR conference on Research and development in information retrieval, page 550--551. New York, NY, USA, ACM, (2004)
A. Markos, M. Vozalis, and K. Margaritis. Artificial Intelligence Applications and Innovations - 6th IFIP WG 12.5 International Conference, AIAI 2010, Larnaca, Cyprus, October 6-7, 2010. Proceedings, volume 339 of IFIP, page 22-29. Springer, (2010)