. 2021 Jun 14;18(12):6431. doi: 10.3390/ijerph18126431
© 2021 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 (https://creativecommons.org/licenses/by/4.0/).
Figure 1.
Flow diagram of cross-over study design.