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. 2013 Aug 12;8(8):e71910. doi: 10.1371/journal.pone.0071910

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© 2013 Chen 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 properly credited.

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SD = standard deviation; IV = weighted mean difference; CI = confidence interval; df = degrees of freedom; Chi² = chi-square statistic; p = p value; I² = I-square heterogeneity statistic; Z = Z statistic; RR = risk ratio; WMD = weight mean difference.