Musibau, Hammed Oluwaseyi, et al. “Electricity Availability, Human Capital Investment and Sustainable Economic Growth Causality in Sub Sahara Africa: Revisited Evidences”. International Journal of Energy Economics and Policy, vol. 9, no. 6, Oct. 2019, pp. 222-33, https://econjournals.com./index.php/ijeep/article/view/8201.