1. Department of Mathematics, Faculty of Science, King Mongkut’s University of Technology, Thonburi (KMUTT), 126 Pracha-Uthit Road, Bang Mod, Thrung Khru, Bangkok 10140, Thailand
2. Department of Mathematics, Islamia College Peshawar, Peshawar 25000, Pakistan
3. Department of Mathematics and Statistics, University of Swat, Mingora 19130, Pakistan