Khaled M. Elbassioni Amr Elmasry Ibrahim Kamel Indexing Schemes for Multi-dimensional Moving Objects. 523-529 2008 Encyclopedia of GIS http://dx.doi.org/10.1007/978-0-387-35973-1_614 reference/gis/2008 db/reference/gis/gis2008.html#ElbassioniEK08