Affiliation: | a Centre for Differential Equations, Continuum Mechanics and Applications, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa b School of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa c Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, South Africa d Centre for Numerical Analysis and Computational Mathematics, South Africa |