ZHENG, Dandan. The Application of Six Sigma Management Theory in Service Industry. International Journal of Global Economics and Management, London, U.K., v. 4, n. 1, p. 275–280, 2024. DOI: 10.62051/ijgem.v4n1.36. Disponível em: https://wepub.org/index.php/IJGEM/article/view/3303. Acesso em: 10 jun. 2026.