Affiliation: | 1. Department of Mathematics, ABa Teacher’s College, Wenchuan, Sichuan 623000, PR China;2. Mathematics Department, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada L2S 3A1;3. Mathematics Department, Purdue University North Central, 1401 S, U.S. 421, Westville, IN 46391, USA |