1. Department of Mathematics, University of the Punjab, 54590 Lahore, Pakistan
2. Department of Mathematics, University of Sargodha, 40100 Sargodha, Pakistan
3. Department of Mathematics, Cankaya University, 06530 Ankara, Turkey
4. Institute of Space Science, Magurele-Bucharest, Romania
5. Lebanese American University, 1102 2801 Beirut, Lebanon