1. Department of Mathematics, COMSATS University Islamabad, Lahore Campus, Pakistan
2. Mathematics Department, Faculty of Science, Taibah University, Al-Madinah Al-Munawarah, Saudi Arabia
3. Department of Sciences and Technology, Ranyah University College, Taif University, P. O. Box 11099, Taif 21944, Saudi Arabia
4. Department of Mathematics, Riphah International University, Lahore, Pakistan