1. Basic Teaching Department of Nantong Open University, Nantong City, Jiangsu Province, China
2. Department of Mathematics, College of Science, University of Duhok, Duhok, Iraq
3. Department of Mathematics, Faculty of Education, Erciyes University, 38039-Melikgazi-Kayseri, Turkey
4. Department of Applied Mathematics, Faculty of Mathematical Sciences, University of Tabriz, Tabriz, Iran