"Prisoner's dilemma: A study in conflict and cooperation" by Anatol Rapoport, Albert S. Chammah, Ann Arbor: The University of Michigan Press, (p. 196), 1965.
The two commands for his computer program,Tit forTat, designed at the University ofToronto. It outperformed all other programs at an international computer tournament in1979, and it continues to excel in tournaments.The programinitiates reciprocal cooperation yet responds in kind to provocation.