It looks as though there is also earlier work on cooperation in one-shot prisoners dilemmas—e.g.:
Harrington, Joseph E. Jr. (1995) Cooperation in a one-shot Prisoners’ Dilemma.
http://www.sciencedirect.com/science/article/pii/S0899825605800065
Heiner, Ronald Asher (2002) Robust Evolution Of Contingent Cooperation In Pure One-Shot Prisoners’ Dilemmas
http://econstor.eu/bitstream/10419/23123/1/2002-09_evolution1.pdf
It looks as though there is also earlier work on cooperation in one-shot prisoners dilemmas—e.g.:
Harrington, Joseph E. Jr. (1995) Cooperation in a one-shot Prisoners’ Dilemma.
http://www.sciencedirect.com/science/article/pii/S0899825605800065
Heiner, Ronald Asher (2002) Robust Evolution Of Contingent Cooperation In Pure One-Shot Prisoners’ Dilemmas
http://econstor.eu/bitstream/10419/23123/1/2002-09_evolution1.pdf