Lewis, David. "Prisoners' Dilemma Is a Newcomb Problem." Philosophical Papers Volume II. : Oxford University Press, 1987-06-11. Oxford Scholarship Online. 2003-11-01. Date Accessed 23 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/0195036468.001.0001/acprof-9780195036466-chapter-11>.
Lewis, D.(1987-06-11). Prisoners' Dilemma Is a Newcomb Problem. In Philosophical Papers Volume II. : Oxford University Press. Retrieved 23 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/0195036468.001.0001/acprof-9780195036466-chapter-11.
Lewis, David. "Prisoners' Dilemma Is a Newcomb Problem." In Philosophical Papers Volume II. : Oxford University Press, 1987-06-11. http://www.oxfordscholarship.com/view/10.1093/0195036468.001.0001/acprof-9780195036466-chapter-11.
Lewis D. Prisoners' Dilemma Is a Newcomb Problem. In: Lewis D. Philosophical Papers Volume II. Oxford University Press; 1987. http://www.oxfordscholarship.com/view/10.1093/0195036468.001.0001/acprof-9780195036466-chapter-11. Accessed May 23, 2013.