J. Henrich, R. Boyd, S. Bowles and C. Camerer. In Search of Homo Economicus: Behavioral Experiments in 15 Small-Scale Societies // American Economic Review. 2001 (91). № 2; D. G. Rand, J. D. Greene and M. A. Nowak. Spontaneous Giving and Calculated Greed // Nature. 2012 (489). № 7416. P. 427–430.