S. Chakrabarti, M. Joshi, and V. Tawde. Proceedings of the 24th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, page 208-216. ACM Press, (2001)
B. Davison. Proceedings of the 26th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, page 367-368. ACM Press, (2003)