Usman, Abubakar, and Nasir Mu'Azu Kontagora. “Statistical Process Control on Production: A Case Study of Some Basic Chemicals Used in Pure Water Production”. Pakistan Journal of Nutrition 9, no. 4 (March 15, 2010): 387–391. Accessed September 6, 2025. https://pjnonline.org/pjn/article/view/1185.