Menstrual cycles shortly after menarche in European and Bantu girls. I. Epidemiological aspects.
D000293:Adolescent; D000353:Africa, Southern; D000367:Age Factors; D044383:Black People; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008598:Menstruation; D009426:Netherlands; D010060:Ovulation; D044465:White People