Greg Aloupis Jean Cardinal Sébastien Collette Stefan Langerman Shakhar Smorodinsky Coloring Geometric Range Spaces. 348-362 2009 41 Discrete & Computational Geometry 2 http://dx.doi.org/10.1007/s00454-008-9116-4 db/journals/dcg/dcg41.html#AloupisCCLS09