get out of knots and into Poincare. Having seen Papakyriakopoulos's work, Haken figured the conjecture "should be immediately possible to prove." Poenaru, his rival, defected from Rumania in 1962 while attending a conference in Sweden, and sought asylum in France. He had made his name while still in B

e Ken Appel four years later. "I shall not go back," he vows, then adds, in a disconcerting way, "unless it's to look for counter-examples." As for Poenaru, when he resumed work on the conjecture recently, one of his colleagues' wives was said to have commented, "Poor Valentin, he's got the bug again."