Template:Ref-Swift1916
From Embryology
Swift CH. Origin of the sex-cords and definitive spermatogonia in the male chick. (1916) Amer. J Anat. 20(1):.
Swift CH. Origin of the sex-cords and definitive spermatogonia in the male chick. (1916) Amer. J Anat. 20(1):.