Every planar map is four colorable
Appel, Kenneth and Haken, Wolfgang
Every planar map is four colorable - Providence American Mathematical Society 1989 - xv, 741p. - Contemporary Mathematics 98 .
511.5 / Ap646.EP
Every planar map is four colorable - Providence American Mathematical Society 1989 - xv, 741p. - Contemporary Mathematics 98 .
511.5 / Ap646.EP
