1. Department of Mathematics, Mirpur University of Science and Technology, Mirpur 10250 (AJK), Pakistan
2. Department of Mathematics, Zhejiang Normal University, Jinhua, People’s Republic of China
3. Department of Mathematics, King Abdulaziz University, Jeddah, Saudi Arabia
4. Department of Mathematics and Statistics, University of South Florida, Tampa, FL, USA
5. School of Mathematical and Statistical Sciences, North-West University, Mafikeng Camus, Private Bag X2046, Mmabatho 2735, South Africa