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Publisher's Note: Minor correction in number of studies

Posted by plosmedicine on 02 Aug 2011 at 21:57 GMT

24
http://plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001056#article1.body1.sec4.p2

Under the Discussion heading, the number of studies analyzed is incorrectly given as 24. This should read 28, as it does elsewhere in the text.

No competing interests declared.