1. Department of Mathematics, COMSATS University Islamabad, Wah Campus, Wah Cantt 47040, Pakistan
2. Department of Mathematics, Abbottabad University of Science and Technology, Abbottabad 22500, Pakistan
3. Department of Mathematics, College of Science, King Saud University, P.O. Box 22452, Riyadh 11495, Saudi Arabia
4. Department of Basic Sciences, College of Science and Theoretical Studies, Saudi Electronic University, Riyadh 11673, Saudi Arabia
5. Department of Mathematics, Government Akhtar Nawaz Khan (Shaheed) Degree College KTS, Haripur 22620, Pakistan
6. Faculty of Science and Technology, University of the Faroe Islands, Vestarabryggja 15, FO 100 Torshavn, Faroe Islands