1. Darwin, C. The Origin of Species by Means of Natural Selection (Murray, London, 1859).
2. Dobzhansky, T. Genetics and the Origins of Species (Columbia Univ. Press, New York, 1937).
3. Mayr, E. Systematics and the Origin of Species (Columbia Univ. Press, New York, 1942).
4. Bush, G. L. in Evolutionary Strategies of Parasitic Insects and Mites (ed. Price, P. W.) 187–206 (Plenum, New York, 1975).
5. Bush, G. L. The Taxonomy, Cytology and Evolution of the Genus Rhagoletis in North America (Museum of Comparative Zoology, Cambridge, Massachusetts, 1966).