Ferraz, D., and F. C. R. de Oliveira. “Impact of the National Professional Qualification Program (PNQ) on Income: An Econometric Analysis in Piracicaba/SP-Brazil”. Research &Amp; Debate Journal of the Postgraduate Program in Political Economy, vol. 28, no. 2(52), Dec. 2017, pp. pg. 105-123, https://revistas.pucsp.br/index.php/rpe/article/view/34838.