. 2017 Jan 20;12(1):e0170246. doi: 10.1371/journal.pone.0170246
© 2017 Liu et al
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Fig 1. Flow chart of included studies in the meta-analysis.
