1. Department of Mathematics, Quaid-i-Azam University, Islamabad, Pakistan
2. Department of Studies and Research in Mathematics, Davangere University, Davangere, India
3. Department of Mathematics, COMSATS University Islamabad, Sahiwal, Pakistan
4. Department of Mathematics and Statistics, Riphah International University I-14, Islamabad, Pakistan
5. Department of Mathematics, College of Sciences, King Khalid University, Abha, Saudi Arabia