1. Department of Mathematics, Faculty of Sciences, HITEC University, Taxila Cantt, Pakistan
2. Department of Mathematics, COMSATS Institute of Information Technology, Attock, Pakistan
3. Department of Mathematics, COMSATS Institute of Information Technology, Abbottabad, Pakistan
4. School of Mathematical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia