O.V. Borodin, A new proof of the 6 color theorem, J. Graph Theory 19, 507-521, 1995.
August 12, 1997. Tommy R. Jensen
J.P. Hutchinson, Three-Coloring Graphs Embedded on Surfaces with All Faces Even-Sided, J. Combin. Theory Ser. B 65, 139-155, 1995.
August 29, 1997. Tommy R. Jensen
C. Thomassen, Grötzsch's 3-Color Theorem and its Counterparts for the Torus and the Projective Plane, J. Combin. Theory Ser. B 62, 268-279, 1994.
August 29, 1997. Tommy R. Jensen
D.A. Youngs, 4-Chromatic Projective Graphs, J. Graph Theory 21, 219-227, 1996.
August 29, 1997. Tommy R. Jensen