Polygenic inheritance of Tourette syndrome, stuttering, attention deficit hyperactivity, conduct and oppositional defiant disorder: the additive and subtractive effect of the three dopaminergic genes - DRD2, D beta H, and DAT1. - Comings,DE.; Wu,S.; Chiu,C.; Ring,RH.; Gade,R.; Ahn,C.; MacMurray,JP.; Dietz,G.; Muhleman,D. (American J Med Genet, 1996)