Genetical, environmental and personality factors influencing the age of first sexual intercourse in twins.
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001290:Attitude; D003075:Coitus; D005260:Female; D006801:Humans; D008131:London; D008297:Male; D008875:Middle Aged; D010551:Personality; D011247:Pregnancy; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic