Riak , D. G. A., and D. B. A. Bill. “MEASUREMENT OF DEVELOPMENT & CAUSES OF UNDERDEVELOPMENT IN AFRICA”. IJRDO - Journal of Social Science and Humanities Research, Vol. 7, no. 8, Aug. 2022, pp. 179-8, http://cpcalendars.ijrdo.org/index.php/sshr/article/view/5263.