Age at menarche: genetic and environmental influences.
D000293:Adolescent; D000367:Age Factors; D044383:Black People; D004777:Environment; D005006:Ethnicity; D005260:Female; D005826:Genetics, Medical; D006801:Humans; D008598:Menstruation; D012424:Rural Population; D012923:Social Class; D013019:South Africa; D014505:Urban Population; D044465:White People