. 2018 Dec 9;15(12):2791. doi: 10.3390/ijerph15122791
© 2018 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.