| Date | Event | Description |
|---|---|---|
| 27 June 2011 | New search has been performed | Issue 8, 2011: Updated searches yielded no new trials. 'Risk of bias' tables completed for included studies and new subheadings activated |
| 16 October 2008 | Amended | Converted to new review format |
| 23 January 2008 | New search has been performed | Updated search in January 2008 found no new trials |
| 14 November 2001 | New citation required and conclusions have changed | Substantive amendment |
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