S. Amer-Yahia, E. Curtmola, and A. Deutsch. SIGMOD '06: Proceedings of the 2006 ACM SIGMOD international conference on Management of data, page 575--586. New York, NY, USA, ACM Press, (2006)
M. Garofalakis, A. Gionis, R. Rastogi, S. Seshadri, and K. Shim. SIGMOD '00: Proceedings of the 2000 ACM SIGMOD international conference on Management of data, 29, page 165--176. New York, NY, USA, ACM Press, (June 2000)