. 2020 Nov 23;17(22):8701. doi: 10.3390/ijerph17228701
© 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.
Topic proportions at the three time points.