1. School of Mathematics, Hangzhou Normal University, Hangzhou 311121, P. R. China
2. Department of Mathematics, Faculty of Science, King Mongkuts, University of Technology Thonburi (KMUTT), 126 Pracha-Uthit Road, Bang Mod, Thrung Khru, Bangkok 10140, Thailand
3. Department of Basic Sciences, University of Engineering and Technology, Peshawar, Khyber Pakhtunkhwa, Pakistan
4. Department of Mathematics and Statistics, University of Swat, Khyber Pakhtunkhawa, Pakistan
5. Department of Computer Engineering, Biruni University, Istanbul, Turkey
6. Department of Mathematics, Near East University, TRNC, Mersin 10, Turkey