Genetic analyses of smoking initiation, persistence, quantity, and age-at-onset of regular cigarette use in Brazilian families: the Baependi Heart Study - Morimoto, Andréa R.V. R; Oliveira, Camila M; Giolo, Suely R; Soler, Júlia Maria Pavan; Andrade, Mariza de; Krieger, José E; Pereira, Alexandre C (BMC Medical Genetics, 2012)