Noga Alon Robert Berke Kevin Buchin Maike Buchin Péter Csorba Saswata Shannigrahi Bettina Speckmann Philipp Zumstein Polychromatic colorings of plane graphs. 338-345 2008 Symposium on Computational Geometry http://doi.acm.org/10.1145/1377676.1377734 conf/compgeom/2008 db/conf/compgeom/compgeom2008.html#AlonBBBCSSZ08