Y. Duan, L. Jiang, T. Qin, M. Zhou, and H. Shum. Proceedings of the 23rd International Conference on Computational Linguistics, page 295--303. Stroudsburg, PA, USA, Association for Computational Linguistics, (2010)
S. Ji, K. Zhou, C. Liao, Z. Zheng, G. Xue, O. Chapelle, G. Sun, and H. Zha. SIGIR '09: Proceedings of the 32nd international ACM SIGIR conference on Research and development in information retrieval, page 35--42. New York, NY, USA, ACM, (2009)