. 2013 Aug 26;13:776. doi: 10.1186/1471-2458-13-776
Copyright © 2013 van Drongelen et al.; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Figure 1.
Study design.