Affiliation: | (1) Department of Mathematics, Zhongkai Agrotechnical College, Guangzhou 510225, China (E-mail: yangfj88@sohu.com), CN;(2) Department of Mathematics and Physics, Wuyi University, Jiangmen 529020, China (E-mail: Chenxm88@sohu.com), CN;(3) Department of Basics, Zhongshan College, Zhongshan 528403, China, CN |