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. 2019 May 22;16(10):1818. doi: 10.3390/ijerph16101818

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© 2019 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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The distribution of the sites with different levels. By referring to the free data obtained from the Ramsar’s official website and conducting relevant calculations and statistics, the authors use the Arcgis 10.2 software to draw Figure 5. The data source is Reference [28].