Open Problem Garden - four colour theorem - Comments http://www.openproblemgarden.org/category/four_colour_theorem Comments for "four colour theorem" en four colour theorem http://www.openproblemgarden.org/category/four_colour_theorem <br /> http://www.openproblemgarden.org/category/four_colour_theorem#comment Thu, 25 Jul 2013 14:26:41 +0200 53820 at http://www.openproblemgarden.org