1. National University of Sciences and Technology, School of Natural Sciences, Department of Mathematics, Islamabad, Pakistan
2. Quaid-i-Azam University, Department of Mathematics, Islamabad, Pakistan + National University of Sciences and Technology, School of Natural Sciences, Department of Mathematics, Islamabad, Pakistan
3. Atilim University, Department of Mathematics, Incek, Ankara, Turkey + King Abdulaziz University, Nonlinear Analysis and Applied Mathematics Research Group (NAAM), Jeddah, Saudi Arabia