1. Hamilton, W. D. Science 156, 477–488 (1967).
2. Hamilton, W. D. in Sexual Selection and Reproductive Competition in Insects (eds Blum, M. S. & Blum, N. A.) 167–221 (Academic, New York, 1979).
3. Wilson, D. S. & Colwell, R. K. Evolution (in the press).
4. Maynard Smith, J. The Evolution of Sex (Cambridge University Press, 1978).
5. Bulmer, M. G. & Taylor, P. D. Nature 284, 448–449 (1980); J. theor. Biol 86, 83–89 (1980).