1. Department of Mathematics, College of Engineering & Science, Victoria University, Melbourne, Australia
2. Department of Mathematics, Faculty of Sciences, HITEC University, Taxila, Pakistan
3. Faculty of Mathematics and Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam
4. Department of Mathematics, College of Arts and Sciences, Prince Sattam bin Abdulaziz University, Wadi Aldawaser, Saudi Arabia