Egbetokun, S., E. S. Osabuohien, and T. Akinbobola. “Feasible Environmental Kuznets and Institutional Quality in North and Southern African Sub-Regions”. International Journal of Energy Economics and Policy, vol. 8, no. 1, Jan. 2018, pp. 104-15, https://www.econjournals.com/index.php/ijeep/article/view/5948.