2David Gauthier. Morality, Rational Choice, and Semantic Representation: A Reply to My Critics, Social Philosophy & Policy, 1987.
3David Gauthier. "Uniting Separate Persons" in Rationality, Justice and the Social Contract, ed. David Gauthier and Robert Sugden , New York: Harvester Wheatsheaf, 1993.
4Matt Ridley, The Origins of Virtue , New York: Viking Penguin, 1997.