Date	Event	Description
12 August 2009	New citation required and conclusions have changed	Updated, new studies found, additions to the methods section, conclusions changed and additional authors contributed to the review.
30 October 2008	Amended	Converted to new review format.
19 July 2004	Amended	Minor update.
2 July 2004	New search has been performed	New studies sought but none found.
30 October 2002	New citation required and conclusions have changed	Substantive amendment.