Professor Hasi Wulan
Department of Mathematics, Shantou University
Shantou, Guangdong 5151063, China
Tel: +86-754-2902029
Fax: +86-754-2903947
E-mail: wulan@stu.edu.cn

Ms Yali Liu
Department of Mathematics, Shantou University
Shantou, Guangdong 5151063, China
Tel: +86-754-2902034
Fax: +86-754-2903947
E-mail: ylliu@stu.edu.cn