Determinants of out-of-pocket health expenditure on children: an analysis of the 2004 Pelotas Birth Cohort - Silva, Marcelo Torres da; Barros, Aluísio J. D.; Bertoldi, Andréa D.; Jacinto, Paulo de Andrade; Matijasevich, Alicia; Santos, Iná S.; Tejada, Cesar Augusto Oviedo (International Journal for Equity in Health, 2015)