Raghavan Dhandapani Jacob E. Goodman Andreas Holmsen Richard Pollack Shakhar Smorodinsky Convexity in Topological Affine Planes. 243-257 2007 38 Discrete & Computational Geometry 2 http://dx.doi.org/10.1007/s00454-007-1336-5 db/journals/dcg/dcg38.html#DhandapaniGHPS07