. 2015 May 1;16:39. doi: 10.1186/s10194-015-0522-8
© Merki-Feld et al.; licensee Springer. 2015
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.
Figure 1.
Flow diagram of the study population.