title: Coital frequency and twinning. A comment.
authors.affiliation: MRC Mammalian Development Unit, University College London.
authors.forename: W H
authors.initials: WH
authors.lastname: James
mesh_terms: D003075:Coitus; D006801:Humans; D015233:Models, Statistical; D013997:Time Factors; D014429:Twins, Dizygotic / Q000706:statistics & numerical data*