. 2020 Sep 12;17(18):6657. doi: 10.3390/ijerph17186657
© 2020 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/).
Figure 1.
PRISMA flowchart of study selection process.