1. Department of Mathematics and Statistics, University of Agriculture, Faisalabad, Pakistan
2. Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu 212013, P. R. China
3. Mathematics Department, Faculty of Science, Taibah University, Al-Madinah Al-Munawarah, Saudi Arabia
4. School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China
5. Department of Mathematics, The University of Lahore, Lahore, Pakistan