Affiliation: | 1. Institute of Mathematics, School of Mathematics and Computer Sciences, Nanjing Normal University, 210097, Jiangsu, PR China;2. College of Mathematics, Changchun Normal University, Changchun 130032, Jilin, PR China;3. College of Mathematics and Physics, Nanjing University of Information Science and Technology, Nanjing, 210044, Jiangsu, PR China |