German-American mathematician who in 1976 submitted the first mathematical proof that depended on computer assistance. This proof, that the four-color map conjecture was true, was a watershed event in mathematics, ushering in an era of proofs increasingly dependent on computers for their success. The four-color map conjecture, which had defied proof for over a century, stated that it was impossible to construct a map that needed more than four colors to make all adjacent regions a different color.