Keywords: Groetzsch graph 4COL.svg The chromatic number of the Grötzsch graph is 4 Layout from David Eppstein File Groetzsch-graph svg Groetzsch-graph svg 2009-08-18 09 08 UTC Groetzsch-graph svg David Eppstein derivative work Koko90 <span class signature-talk >talk</span> Groetzsch-graph svg </nowiki> Uploaded with derivativeFX Grötzsch graph |