1. Department of Mathematics, Quaid-I-Azam University, Islamabad, Pakistan
2. Department of Mathematical Sciences, Federal Urdu University of Arts, Sciences & Technology, Islamabad, Pakistan
3. Department of Mathematics and Sciences, College of Humanities and Sciences, Prince Sultan University, Riyadh, Saudi Arabia
4. Department of Mathematics, Air University, Islamabad, Pakistan
5. Department of Mathematics, College of Sciences, King Khalid University, Abha, Saudi Arabia
6. Department of Mathematics, Faculty of Science, The Hashemite University, Zarqa, Jordan