1. Mythology and customs associated with twins;Corney,1975
2. Introduction;MacGillivray,1988
3. Aetiology of twinning;Campbell,1988
4. Twins with two different fathers identified by HLA;Teraski;New Engl J Med,1978
5. Increased monozygotic twinning rate after ovulation induction;Derom;Lancet,1987