J. Haunert, K. Anders, and M. Sester. Proceedings of the ISPRS Workshop on Multiple Representation and Interoperability of Spatial Data, February 22--24, 2006, Hannover, Germany, volume XXXVI(Part 2/W40) of International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, page 49--57. ISPRS, (2006)
S. Kashyap, S. Deb, K. Naidu, R. Rastogi, and A. Srinivasan. PODS '06: Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems, page 308--317. New York, NY, USA, ACM Press, (2006)