Ferraz, D. y Oliveira, F.C.R. de 2017. Impact of the National Professional Qualification Program (PNQ) on Income: An Econometric Analysis in Piracicaba/SP-Brazil. Pesquisa & Debate Revista do Programa de Estudos Pós-Graduados em Economia Política. 28, 2(52) (dic. 2017), pg. 105–123.