Authors
Tian Lu
Dept. of Math. and Physics, North China Electric power university, Beijing, China
Zhongyan Li
Dept. of Math. and Physics, North China Electric power university, Beijing, China
© 2018 Tian Lu, Zhongyan Li, published by Xi’an Technological University
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.