1. Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box 80203, Jeddah 21589, Saudi Arabia
2. Department of Applied Mathematics and Statistics, Technical University of Cartagena, Hospital de Marina, 30203 Cartagena, Spain
3. Department of Mathematics and Statistics, Hazara University, Mansehra, Pakistan
4. Departamento de Anatomía Humana y Psicobiologia, University of Murcia, 30100 Murcia, Spain