. 2017 Jun 16;96(24):e7140. doi: 10.1097/MD.0000000000007140
Copyright © 2017 the Author(s). Published by Wolters Kluwer Health, Inc.
This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. http://creativecommons.org/licenses/by/4.0
Figure 4.
Funnel plot showing publication bias.