Kwang-Su Yang Ruixin Yang Jiang Tang Menas Kafatos An Efficient Method to Find Area Clusters with Constraints Using Grid Index Structure. 433-434 2004 conf/ssdbm/2004 SSDBM http://doi.ieeecomputersociety.org/10.1109/SSDBM.2004.14 db/conf/ssdbm/ssdbm2004.html#YangYTK04