1.Allen, G (1981): The twinning and fertility paradox. In Gedda, L, Parisi, P, Nance, WE (eds): Twin Research 3: Twin Biology and Multiple Pregnancy. New York: Alan R. Liss, pp. 1–13.
2.Allen, G, Parisi, P (1990): Trends in monozygotic and dizygotic twinning rates by maternal age and parity — Further analysis of Italian data, 1949-1985, and rediscussion of US data, 1964-1985. Acta Genet Med Gemellol 39:317–328.
3.Anderson, WW, King, CE (1970): Age-specific selection. Proc US Nat Acad Sci 66:780–786.
4.Boklage, CE (1990): Survival probability of human conceptions from fertilization to term. Int J Fertil 35:75–94.
5.Bulmer, MG (1970): The Biology of Twinning in Man. Oxford: Clarendon Press.
6.Eriksson, AW (1964): Pituitary gonadotrophin and dizygotic twinning. Lancet 2:1298–1299.
7.Eriksson, AW (1973): Human twinning in and around the Alan Islands. Commentationes Biologicae 64:1–159.
8.Eriksson, AW (1990): Twinning in families of triplets. Acta Genet Med Gemellol 39:279–293.
9.Eriksson, AW, Fellman, JO (1967): Twinning and legitimacy. Hereditas 57:395–402.
10.Eriksson, AW, Fellman, JO (1973): Differences in the twinning trends between Finns and Swedes. Am J Hum Genet 25:141–151.
11.Fellman, JO, Eriksson, AW (1987): Statistical models for the twinning rate. Acta Genet Med Gemellol 36:297–312.
12.Fellman, JO, Eriksson, AW (1990): Standardization of the twinning rate. Hum Biol 62:803–816.
13.Heuser, RL (1967): Multiple births, United States - 1964. Washington: US Government Printing Office (Public Health Service Publication No. 1000, Series 21, No. 14).
14.Hull, CL, Hovland, CI, Ross, RT, Hall, M, Perkins, DT, Fitch, FB (1940): Mathematico-Deductive Theory of Rote Learning. A study in Scientific Methodology. New Haven: Yale University Press.
15.James, WH (1984): Coitus-induced ovulation and its implications for estimates of some reproductive parameters. Acta Genet Med Gemellol 33:547–555.
16.La Ferla, JJ, Labrum, H, Tang, K (1982): Psychoendocrine response to sexual arousal in human females, in Prill, HI, Stauber, MN (eds): Advances in Psychosomatic Obstetrics/Gynecology. Berlin, New York: Springer-Verlag, p. 209.
17.Lynn, M (1989): Race differences in sexual behavior: A critique of Rushton and Bogaert's evolutionary hypothesis; and, Criticisms of an evolutionary hypothesis about race differences: a rebuttal to Rushton's reply. J Res Person 23:1–6, 21–34.
18.MacArthur, RH, Wilson, EO (1967): The theory of Island Biogeography. Princeton, NJ: Princeton University Press.
19.Nylander, PPS (1981): The factors that influence twinning rates. Acta Genet Med Gemellol 30:189–202.
20.Parisi, P, Caperna, G (1982): Twinning rates, fertility, and industrialization: a secular study. Proceedings of the Sixth International Congress of Human Genetics, Jerusalem, 1981. New York: Alan R Liss, pp. 375–394.
21.Peller, S (1944): Studies on mortality since the Renaissance. D. Twins and singletons. Bull Hist Med 16:362–381.
22.Rushton, JP (1985): Differential K theory: The sociobiology of individual and group differences. Person Individ Diff 6:441–452.
23.Rushton, JP (1987): Toward a theory of human multiple birthing: sociobiology and r/K reproductive strategies. Acta Genet Med Gemellol 36:289–296.
24.Rushton, JP (1988): Race differences in behaviour: a review and evolutionary analysis. Person Individ Diff 9:1009–1024.
25.Weinberg, W (1901–1902): Beiträge zur Physiologie und Pathologie der Mehrlingsgeburten beim Menschen. Arch Ges Physiol 88:346–430.
26.Wyshak, G (1981): Reproductive and menstrual characteristics of mothers of multiple births and mothers of singletons only: A discriminant analysis. In Gedda, L, Parisi, P, Nance, WE (eds): Twin Research 3, Part A, Twin Biology and Multiple Pregnancy, New York: Alan R Liss, pp 95–105.
27.Zuckerman, M, Brody, N (1988): Oysters, rabbits and people: A critique of “Race differences in Behavior” by J.P. Rushton. Person Individ Diff 9:1025–1033.