1. Department of Mathematics, Faculty of Physical Sciences, Ahmadu Bello University, Zaria, Nigeria
2. Department of Mathematics, Government College University, Faisalabad, Pakistan
3. Department of Mathematics, Çankaya University, Ankara, Turkey
4. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan
5. Department of Mathematics, King Abdulaziz University, Jeddah, Saudi Arabia
6. Department of Mathematics and Statistics, College of Science, Taif University, P.O.Box 11099, Taif 21944, Saudi Arabia