1. Department of Mathematics, Government College University, Katchery Road, Lahore 54000, Pakistan
2. Department of Mathematics and Applied Mathematics, University of Pretoria, Hatfield 002, Pretoria, South Africa
3. Department of Sciences and Humanities, National University of Computer and Emerging Sciences, Lahore Campus, Pakistan
4. Department of Mathematics, Babeș-Bolyai University, Cluj-Napoca, Romania
5. Academy of Romanian Scientists, Bucharest, Romania