Institution: | 1. Department of Mathematics, Humanities and Science and Technology of Hunan, Loudi, Hunan, 417000, China;2. School of Mathematics and Computing Technology, Central South University, Changsha, 410083, China;3. Department of Mathematics, National University of Singapore, 2 Science Drive 2, Singapore, 117543, Republic of Singapore;4. Department of Mathematics, University of Texas-Pan American, Edinburg, TX 78539, USA |