1. Allen G, Harvald B, Shields J (1967) Measures of twin concordance. Acta Genet (Basel) 17:475?481
2. Bammer H, Schaltenbrand G, Solcher H (1960) Zwillingsuntersuchungen bei multipler Sklerose. Dtsch Z Nervenheilkd 181:261?279
3. Bobowick AR, Kurtzke JF, Brody JA, Hrubec Z, Gillespie M (1978) Twin study of multiple sclerosis: an epidemiological enquiry. Neurology 28:978?987
4. Boklage CE (1981) On the timing of monozygotic twinning events. In: Gedda L, Parisi P, Nance WE (eds) Twin research 3: twin biology and multiple pregnancy. Liss, New York, pp 155?165
5. Boklage CE (1990) Surival probability of human conceptions from fertilisation to term. Int J Fertil 35:75?94