1. Department of Mathematical Sciences, University of South Africa, UNISA 0003, South Africa
2. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 110122, Taiwan
3. Department of Mathematics, University of Sistan and Baluchestan, Zahedan, Iran
4. Department of Mathematics, Islamic Azad University, Jouybar Branch, Jouybar, Mazandaran, Iran
5. Department of Civil and Environmental Engineering, Seoul National University, Seoul, South Korea