@techreport{NBERw12097,
 title = "Friend or Foe? A Natural Experiment of the Prisoner's Dilemma",
 author = "John A. List",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Working Paper Series",
 number = "12097",
 year = "2006",
 month = "March",
 URL = "http://www.nber.org/papers/w12097",
}