Long Zhang Ying Li Fangyan Rao Xiulan Yu Ying Chen Dong Liu An Approach to Enabling Spatial OLAP by Aggregating on Spatial Hierarchy. 35-44 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2737&spage=35 2003 conf/dawak/2003 DaWaK db/conf/dawak/dawak2003.html#ZhangLRYCL03