. 2018 Oct 26;15(11):2375. doi: 10.3390/ijerph15112375
© 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 2.
The variability of the studies’ objectives.