E. Gaussier, and C. Goutte. Proceedings of the 28th annual international ACM SIGIR conference on Research and development in information retrieval, page 601--602. New York, NY, USA, ACM, (2005)
M. Girolami, and A. Kabán. Proceedings of the 26th annual international ACM SIGIR conference on Research and development in informaion retrieval, page 433--434. ACM, (2003)