ISMAIL, Azimah et al. DMAIC Six Sigma Methodology in Petroleum Hydrocarbon Oil Classification. International Journal of Engineering and Technology, [S. l.], v. 7, n. 3.14, p. 98–106, 2018. DOI: 10.14419/ijet.v7i3.14.16868. Disponível em: https://sciencepubco.com/index.php/IJET/article/view/16868.. Acesso em: 18 apr. 2025.