Affiliation: | a Institute of Nonlinear Complex Systems, College of Science, China Three Gorges University, Yichang City 443002, Hubei Province, PR China b School of Sciences and Technology, University of New England, Armidale, NSW, 2351, Australia c Department of Mathematics, College of William and Mary, Williamsburg, VA 23187-8795, USA d School of Mathematics, Harbin Normal University, Harbin 150080, Helongjiang, PR China |