Authors
Nina Huo
Department of Mathematics, Yunnan University, Yunnan, China
Bing Li
School of Mathematics and Computer Science, Yunnan Nationalities University, Yunnan, China
© 2020 Nina Huo, Bing Li, Yongkun Li, published by University of Zielona Góra
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.