1. Department of Mathematics, University of the Punjab, Lahore, Pakistan
2. Department of Mathematics, University of Engineering and Technology, Lahore, Pakistan
3. Department of Mathematics, Cankaya University, 06790 Ankara, Turkey
4. Institute of Space Sciences, 077125 Magurele-Bucharest, Romania
5. Department of Medical Research, China Medical University Hospital, China Medical University, 40447 Taichung, Taiwan