Funding for this research was provided by:
Division of Mathematical Sciences (DMS-1812930)
Natural Science Foundation of China (11461011)
Natural Science Foundation of Guangxi Province (2017GXNSFDA198014, 2018GXNSFDA050014)
Article History
Received: 13 July 2020
Revised: 28 November 2020
Accepted: 30 November 2020
First Online: 1 January 2021