Oni, Joe Oladosu, and Bukola Olalekan Bolaji. “Development of a Universal DC Power Supply Using Solar Photovoltaic, Utility and Battery Power Sources”. Journal of Energy in Southern Africa, vol. 22, no. 1, Feb. 2011, pp. 12-17, doi:10.17159/2413-3051/2011/v22i1a3199.