Retrieved December 13, 2014. ↑ Mackenzie, Dana (July 5, 2002), "Mathematics: Graph theory uncovers the roots of perfection", Science, 297 (5578): 38, doi:10.1126/science.297.5578.38, PMID 12098683 . ↑ Cornuéjols, Gérard (2002), "The strong perfect graph conjecture", Proceedings of the International Congress of Mathematicians, Vol.