Eyal Ackerman Oswin Aichholzer Balázs Keszegh Improved upper bounds on the reflexivity of point sets. 241-249 2009 42 Comput. Geom. 3 http://dx.doi.org/10.1016/j.comgeo.2008.05.004 db/journals/comgeo/comgeo42.html#AckermanAK09