1. Ayala, F. J. (1982). Population and evolutionary genetics. Benjamin/Cummings, Menlo Park, California
2. Ayala, F. J., Hedgecock, D., Zumwalt, G. S., Valentine, J. W. (1973). Genetic variation inTridacna maxima, an ecological analog of some unsuccessful evolutionary lineages. Evolution, Lawrence, Kansas 27: 177?191
3. Berger, E. M. (1973). Gene-enzyme variation in three sympatric species ofLittorina. Biol. Bull. mar. biol. Lab., Woods Hole 145: 83?90
4. Berger, E. M. (1983). Population genetics of marine gastropods and bivalves In: Russell-Hunter, W. D. (ed.) The Mollusca. Vol. 6. Ecology. Academic Press, New York, p. 563?596
5. Brandt, (1835). Prodromus descriptionis. Animalium Abh., Mertensio Observatorum. Fascic. I. (polypos, acalephas discophoras et siphonophoras nec non Echinodermata contineus). p. 270 [cited after Verrill (1914)]