1. College of Mathematics and Computer Science, Zhejiang Normal University, China
2. Department of Mathematics and Statistics Hazara University Mansehra, Pakistan
3. Department of Mathematics, Faculty of Arts and Sciences, Yildiz Technical University, Esenler, 34210 Istanbul, Turkey
4. Faculty of Organizational Sciences, University of Belgrade, Belgrade, Serbia
5. Department of Mathematics, University of Gondar, P.O. Box: 196, Gondar, Ethiopia