. 2016 Jul 31;2016:8949835. doi: 10.1155/2016/8949835
Copyright © 2016 Hui Wang et al.
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Figure 1.
PRISMA 2009 flow diagram [12].