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 Press, (2007)
K. Chakrabarti, V. Ganti, J. Han, and D. Xin. SIGMOD '06: Proceedings of the 2006 ACM SIGMOD international conference on Management of data, page 371--382. New York, NY, USA, ACM Press, (2006)