1. School of Mathematics and Information Sciences, Guangzhou University, Guangzhou, China
2. Department of Mathematics, Islamabad Model College for Girls, Islamabad, Pakistan
3. BORDA Research Unit and Multidisciplinary Institute of Enterprise (IME), University of Salamanca, Salamanca, Spain
4. School of Mathematics and Information Sciences, Guangzhou University, Guangzhou, China; Guangzhou Vocational College of Science and Technology, Guangzhou, Guangdong, China
5. School of Mathematics and Statistics, Huazhong University of Science and Technology, Wuhan, PR China; Department of Mathematics, Mirpur University of Science and Technology, Mirpur (AJK), Pakistan