1. Department of Mathematics, Shahid Chamran, University of Ahvaz, Ahvaz, Iran
2. Department of Mathematics, Faculty of Sciences, Gazi University, Ankara, Turkey
3. Department of Computer Engineering, Faculty of Engineering, Ostim Technical, University, Ankara, Turkey
4. Department of Mathematics, The University of Danang — University of Science, and Education, 459 Ton Duc Thang, DaNang City, Vietnam
5. Department of Mathematics, College of Education, Hue University, 34 Le Loi, Hue City, Vietnam