Y. Xie, and P. Yu. Proceedings of the 20th ACM international conference on Information and knowledge management, page 1795--1804. New York, NY, USA, ACM, (2011)
X. Dong, and A. Halevy. SIGMOD '07: Proceedings of the 2007 ACM SIGMOD international conference on Management of data, page 43--54. New York, NY, USA, ACM, (2007)