?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aulast=Stewart&rft.aufirst=AJ&rft.au=Stewart%2C+AJ&rft.date=9+December+2014&rft.atitle=Collapse+of+cooperation+in+evolving+games&rft.volume=111&rft.issue=49&rft.title=Proceedings+of+the+National+Academy+of+Sciences&rft.issn=1091-6490&rft.pages=17558-17563&rft.genre=article