1. Abbott, R J. 1985. Maintenance of a polymorphism for outcrossing frequency in a predominantly selfing plant. In: Haeck, J. and Woldendorp, J. (eds.) Structure and Functioning of Plant Populations II Phenotypic and Genotypic Variation in Plant Populations. North-Holland. pp. 277–286.
2. Antonovics, J, and Ellstrand, N C. 1984. Experimental studies of the evolutionary significance of sexual reproduction. I. A test of the frequency-dependent selection hypothesis. Evolution, 38, 103–115.
3. Bell, G. 1982. The Masterpiece of Nature: The Evolution and Genetics of Sexuality. Croom Helm, London.
4. Burtt, B L. 1977. Aspects of diversification in the capitulum. In: Hey wood, V. H., Harborne, J. B. and Turner, B. L. (eds.) The Biology and Chemistry of the Compositae. Vol. 1. Academic Press, London, pp. 41–59.
5. Charlesworth, B. 1980. The cost of sex in relation to mating system. J Theor Biol, 84, 655–671.