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Publisher's Note: Correction to Figure 2

Posted by PLOS_ONE_Group on 17 Sep 2009 at 22:15 GMT

Summary of literature search and study selection.
http://plosone.org/article/info:doi/10.1371/journal.pone.0006914#pone-0006914-g002

Figure 2 appears incorrectly. A correct version of the figure can be viewed here: http://www.plosone.org/corrections/pone.0006914.g002.cn.tif

No competing interests declared.