1. Department of Mathematics & Statistics, Faculty of Sciences, International Islamic University, Islamabad 44000, Pakistan
2. Center for Modeling & Computer Simulation, Research Institute, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
3. Department of Mathematics and Computer Science, Transilvania University of Brașov, 500036 Brașov, Romania
4. Academy of Romanian Scientists, 030167 Bucharest, Romania