Author(s): |
Guangfeng Zhao, Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China Hongli Wang, Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China Yufen Feng, Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China Haiyan Fan, Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China |