Girmay, Maseapei Elizabeth, and Delson Chikobvu. “Quantifying South Africa’s Sulphur Dioxide Emission Efficiency in Coal-Powered Electricity Generation by Fitting the Three-Parameter Log-Logistic Distribution”. Journal of Energy in Southern Africa, vol. 28, no. 1, Mar. 2017, pp. 91-103, doi:10.17159/2413-3051/2017/v28i1a1530.