Affiliation: | 1. Department of Mathematical Sciences, Federal University of Technology, Akure, Ondo State PMB 704, Nigeria;2. Institute for Groundwater Studies, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein 9300, South Africa;3. CONACyT-Tecnológico Nacional de México/CENIDET, Interior Internado Palmira S/N, Col. Palmira, Cuernavaca, Morelos C.P. 62490 México |