. 2019 Nov 2;16(21):4266. doi: 10.3390/ijerph16214266
© 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/).
Figure 1.
Flow diagram of the study selection process.