1. Cunningham, J. T. Sexual Dimorphism in the Animal Kingdom (Black, London, 1900).
2. Hendrick, A. V. & Temeles, E. J. Trends Ecol. Evol. 4, 136–139 (1989).
3. Gerhardt, U. Zool, Anz. 86, 80–82 (1930).
4. Elgar, M. A., Ghaffar, N. & Read, A. J. Zool. 222, 455–470 (1990).
5. Darwin, C. A. Monograph on the Cirripedia (Royal Society, London, 1851).