Abbas Bahia, Taher Hameed, y Hinwa Hussein Ahmed, Afrah Raheem Idan. «Applying Six Sigma (SS) to Improve the Quality of Academic Life (QAL)». Opción 35, no. 89 (julio 30, 2019): 289-309. Accedido junio 29, 2025. https://mail.produccioncientificaluz.org/index.php/opcion/article/view/24417.