Kenneth Weiss Leila De Floriani Riccardo Fellegara Marcelo Velloso The PR-star octree: a spatio-topological data structure for tetrahedral meshes. 92-101 2011 GIS http://doi.acm.org/10.1145/2093973.2093987 conf/gis/2011 db/conf/gis/gis2011.html#WeissFFV11