1. Darwin, C. R. (1859) On the Origin of Species by Means of Natural Selection, or the Preservation 1 of the Favoured Races in the Struggle for Life, John Murray, London.
2. Hamilton, W. D. (1964) J. Theor. Biol., 7, 1–52.
3. Hamilton, W. D. (1970) Nature, 228, 1218–1220.
4. Trivers, R. L. (1971) Quart. Rev. Biol., 46, 35–57.
5. Wilson, E. O. (1975) Sociobiology, The New Synthesis, Harvard University Press, Cambridge.