Sarpong-Streetor, R. M. N. Y., R. A. Sokkalingam, M. bin Othman, D. L. C. Ching, and H. bin Sakidin. “A Hybrid Autoregressive Integrated Moving Average-PhGMDH Model to Forecast Crude Oil Price”. International Journal of Energy Economics and Policy, vol. 9, no. 5, July 2019, pp. 135-41, https://econjournals.com/index.php/ijeep/article/view/7987.