A recent simplification of the Four Colour Theorem proof, by Robertson, Sanders, Seymour and Thomas, has removed the cloud of doubt hanging over the complex original proof of Appel and Haken. The programs can now be obtained by ftp and easily checked over for correctness. Also the paper part of the proof is easier to verify. This new proof, if correct, should dispel all reasonable criticisms of the validity of the proof of this theorem. References K. Appel and W. Haken.
Every planar map is four colorable.
Bulletin of the American Mathematical Society, vol. K. Appel and W. Haken. Every planar map is four colorable. Illinois Journal of Mathematics, vol. The Four Colour Theorem Preprint, February 1994.