1. Department of Mathematics, National Kaohsiung Normal University, Kaohsiung 82444, Taiwan
2. Department of Mathematics Education, National Taichung University of Education, Taichung 403, Taiwan
3. Faculty of Technical Sciences, University of Novi Sad, Trg D. Obradovića 6, 21125 Novi Sad, Serbia
4. Department of Mathematics, College of Science, King Saud University, Riyadh 11451, Saudi Arabia