Yahaya, M., S. L. Lim, A. I. Ibrahim, W. C. Yeong, and K. W. Khaw. “OPTIMAL DESIGNS OF THE VARIABLE PARAMETERS X ̄ CHART WITH ESTIMATED PROCESS PARAMETERS”. International Journal of Industrial Engineering: Theory, Applications and Practice, vol. 28, no. 3, Nov. 2021, doi:10.23055/ijietap.2021.28.3.7081.