1. Placenta praevia and sex at birth;MacGillivray, I.; Davey, D.; Isaacs, S.,1986
2. Gender of infants conceived on different days of the menstrual cycle;Harlap, S.;N Engl 7 Med,1979
3. Use ofcontraceptives prior to and after conception and exposure to other fetal hazards;Shiono, P.H.; Harlap, S.; Ramcharan, S.; Berendes, H.; Gupta, S.; Pellegrin, F.;Contraception,1979
4. The women and their pregnancies;Niswander, K.R.; Gordon, M.,1972