Alege, P. O., O. S. Adediran, and A. A. Ogundipe. “Pollutant Emissions, Energy Consumption and Economic Growth in Nigeria: A Multivariate Granger Causality Framework”. International Journal of Energy Economics and Policy, vol. 6, no. 2, Apr. 2016, pp. 202-7, https://www.econjournals.com/index.php/ijeep/article/view/1441.