1. Atz, J. W., 1962, Effects of hybridization on pigmentation in fishes of the genus Xiphophorus, Zoologica 47: 153–181.
2. Bao, I., 1981, The genetic and endocrine control of sexual maturation and sterility in hybrids between Xiphophorus belleri and X. maculatus, Ph. D. dissertation, New York University, New York.
3. Borowsky, R. L., 1969, Ecological and social factors influencing the polymorphic pigmentation systems of Xiphophorus v. variatus (Pisces: Poeciliidae), Ph. D. dissertation, Yale University, New Haven, Connecticut.
4. Borowsky, R. L., 1973a, Relative size and the development of fin coloration in Xiphophorus variatus, Physiol. Zool. 46: 22–28.
5. Borowsky, R. L., 1973b, Social control of adult size in males of Xiphophorus variatus, Nature 245: 332–335.