Erin W. Chambers Éric Colin de Verdière Jeff Erickson Francis Lazarus Kim Whittlesey Splitting (complicated) surfaces is hard. 94-110 2008 41 Comput. Geom. 1-2 http://dx.doi.org/10.1016/j.comgeo.2007.10.010 db/journals/comgeo/comgeo41.html#ChambersVELW08