Zhan Chen Jing Ding Mu Zhang Wallapak Tavanapong Johnny S. Wong Hierarchical Clustering-Merging for Multidimensional Index Structures. 81-90 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2728&spage=81 2003 conf/civr/2003 CIVR db/conf/civr/civr2003.html#ChenDZTW03