1. Institute of Computing Science and Technology, Guangzhou University, Guangzhou 510006, China
2. School of Computer Science of Information Technology, Qiannan Normal University for Nationalities, Duyun 558000, China
3. Department of Mathematics and Natural Sciences, Prince Mohammad Bin Fahd University, P.O. Box 1664, Al Khobar 31952, Saudi Arabia
4. Department of Mathematics, Zonguldak Bülent Ecevit University, Zonguldak 67100, Turkey
5. Department of Mathematics, Hannam University, Daejeon 34430, Republic of Korea