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Authors
Liu, Shun Jia
Xu, Xin Long https://orcid.org/0000-0003-1023-9069
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Funding
Funding for this research was provided by:
National Social Science Foundation of China (19BJY170)
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Article History
Received: 18 August 2020
Accepted: 22 November 2020
First Online: 6 January 2021
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: The code used and/or analyzed by Stata and MATLAB software during the current study is available from the supplemental materials.
: The submitted paper has not been published previously, that it is not under consideration for publication elsewhere, that its publication is approved by all authors and tacitly or explicitly by the responsible authorities where the work was carried out, and that, if accepted, it will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright-holder.
: All authors read and approved the final manuscript.
