On reducibility in the four color problem
Hassler Whitney · Birkhäuser Boston eBooks · 1992
Quite recently, Y. Shimamoto showed (Report, AMD 618, Brookhaven National Laboratory) that the four color map theorem would be proved if a certain configuration H of H. Heesch were proved “D-reducible.” A computer program has been run (considering nearly 200,000 different colorings of the boundary C of H, each one a complicated problem); the computer said “yes.” I am told that the computer was asked the wrong question.