James Vanderhyde Andrzej Szymczak Topological simplification of isosurfaces in volumetric data using octrees. 16-31 2008 70 Graphical Models 1-2 http://dx.doi.org/10.1016/j.gmod.2007.06.002 db/journals/cvgip/cvgip70.html#VanderhydeS08