| Date | Event | Description |
|---|---|---|
| 11 February 2009 | New citation required but conclusions have not changed | Review updated May 2008 |
| 4 May 2008 | New search has been performed | New studies identified and major update completed |
| 31 March 2008 | Amended | Converted to new review format. |
| 28 February 2002 | New citation required and conclusions have changed | Substantive amendment |
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