1. Department of Mathematical Sciences, United Arab Emirates University, P.O. Box 15551, Al Ain, UAE
2. School of Natural Sciences (SNS), National University of Sciences and Technology (NUST), Sector H-12, Islamabad, Pakistan
3. Department of Mathematics, University of Lahore, Pakpattan Campus, Pakistan
4. Department of Mathematics, COMSATS Institute of Information Technology, Attock Campus, Pakistan