Keywords: Hadwiger-Nelson.svg Hadwiger “Nelson problem 7-coloring of the plane and 4-chromatic unit distance graph self-made originally for http //www ics uci edu/~eppstein/junkyard/color html The Geometry Junkyard 1996-07-17 David Eppstein Graph coloring Hexagonal tilings Discrete geometry Moser spindle Files by User David Eppstein from en wikipedia Order-3 hexagonal tiling |