1. Darwin, C. The Descent of Man, and Selection in Relation to Sex (Murray, London, 1871).
2. Fisher, R. A. The Genetical Theory of Natural Selection (Clarendon, Oxford, 1930).
3. Trivers, R. L. in Sexual Selection and the Descent of Man (ed. Campbell, B.) 136–179 (Heinemann, London, 1972).
4. Halliday, T. R. in Mate Choice (ed. Bateson, P.) 3–32 (Cambridge University Press, 1983).
5. LeCroy, M., Kulupi, A. & Peckover, W. S. Wilson Bull. 92, 289–301 (1980).