| Date | Event | Description |
|---|---|---|
| 16 April 2013 | New citation required but conclusions have not changed | New studies added, conclusions unchanged. |
| 7 September 2012 | New search has been performed | Search updated to 31 January 2012. New studies added, conclusions unchanged. |
| 30 August 2011 | New search has been performed | Converted to new review format. Updated search till 31 December 2010. New studies, conclusions changed. |
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