Lecture #7 was an introduction to multiagent interaction.
Much has been written on the Prisoner's Dilemma. The clasic reference is still Axelrod's book:
R. Axelrod, The Evolution of Cooperation, Basic Books.and anyone interested in the PD is well advised to beg, borrow, or steal a copy (and then read it, of course).
For those who can't lay their hands on a copy, this article:
R. Axelrod and W. D. Hamilton The Evolution of Cooperation, Science, 211, March 27th, 1390-1396, 1981.is a good second. It is one of the early articles that Axelrod wrote following the tournament.
Another good description of Axelrod's tournament can be found in:
D. Hofstadter, "The Prisoner's Dilemma Computer Tournaments and the Evolution of Cooperation", in Metamagical Themas: Questing for the Essence of Mind and Pattern, (D. Hofstadter, Penguin, 1986), 715-734.while:
W. Poundstone, Prisoner's Dilemma, Oxford University Press, 1992.not only discusses the PD, but also talks about the early history of game theory.