Gabriela Araujo Adrian Dumitrescu Ferran Hurtado Marc Noy Jorge Urrutia On the chromatic number of some geometric type Kneser graphs. 59-69 2005 32 Comput. Geom. 1 http://dx.doi.org/10.1016/j.comgeo.2004.10.003 db/journals/comgeo/comgeo32.html#AraujoDHNU05