WU, Shuang; TANG, Hong. Six Sigma in the Service Industry. International Journal of Global Economics and Management, London, U.K., v. 4, n. 2, p. 329–334, 2024. DOI: 10.62051/ijgem.v4n2.36. Disponível em: https://wepub.org/index.php/IJGEM/article/view/3715. Acesso em: 19 jun. 2026.