| Date | Event | Description |
|---|---|---|
| 31 July 2011 | New search has been performed | An update search was performed for this review on 31 July 2011. New studies were identified for both inclusion and exclusion within the review. |
| 6 November 2008 | Amended | Converted to new review format. |
| 6 February 2005 | New citation required and conclusions have changed | The review has been substantially updated and rewritten following the publication of three new trials. |
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