Usen, J. E., E. J. Okoi, E. M. Egomo, E. N. Henshaw, and E. B. Hogan. “A Critique on the Foundational Response Surface Methodology for Exploring Optimal Regions”. Asian Journal of Probability and Statistics, Vol. 8, no. 2, July 2020, pp. 1-16, doi:10.9734/ajpas/2020/v8i230201.