Guo, Qingchun http://orcid.org/0000-0002-0097-0168
He, Zhenfang
Funding for this research was provided by:
National Natural Science Fund of China (41572150, 41472162, 41702373)
Shandong Social Sciences Planning Research Fund (18CKPJ34)
Shandong Province Higher Educational Humanities and Social Science Fund (J18RA196)
State Key Laboratory of Loess and Quaternary Geology Found (SKLLQG1907)
Article History
Received: 16 September 2020
Accepted: 1 December 2020
First Online: 7 January 2021
Compliance with ethical standards
:
: The authors declare that they have no competing interests.
: All data were obtained with the agreement of world health organization (WHO). The data in this article are obtained from an open database of the World Health Organization (links are provided in the resources section). These can be accessible locally for educational purposes.
: Not applicable.
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