C. Liu, R. White, and S. Dumais. Proceedings of the 33rd international ACM SIGIR conference on Research and development in information retrieval, page 379--386. ACM, (2010)
X. Liu, X. Kong, and Y. Li. Proceedings of the 25th ACM International on Conference on Information and Knowledge Management, page 2179--2184. New York, NY, USA, ACM, (2016)