Bergstrom, Carl T.Bronstein, Judith L.Bshary, RedouanConnor, Richard C.Daly, MartinFrank, Steven A.Gintis, HerbertKeller, LaurantLeimar, OlofNoe, RonaldQueller, David C.2004-11-012007-06-132004-11-012007-06-132003Bergstrom et al. 2003. Chapter 13 in P. Hammerstein, ed., Genetic and Cultural Evolution of Cooperation Cambridge: MIT Press0262083264http://hdl.handle.net/1773/199586500 bytesapplication/pdfenmutualismevolutionsybiosiscooperationreciprocityBook chapter