| Date | Event | Description |
|---|---|---|
| 10 July 2012 | New citation required and conclusions have changed | The search has been updated to 9 March 2012, and two new studies have been added. Graphical representations of the 'Risk of bias', a 'Summary of findings' table and a 'Study flow diagram' have been added. The conclusions have changed (minor). |
| 9 March 2012 | New search has been performed | The search for studies has been updated to 9 March 2012. Two new studies have been included. |
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