Date	Event	Description
25 June 2008	Feedback has been incorporated	Feedback from Vasiliy Vlassov added.
23 June 2008	Amended	Converted to new review format.
30 April 2006	New citation required and minor changes	New author.
30 June 2005	New search has been performed	Search updated. New studies were added to the Background and Implications for research sections, expanding these sections; one new trial was added (Wolfe 1999) and one trial, previously included, was removed pending clarification of further information received from the authors of the trial (Lee 1996a); one study which was included only as an abstract in a previous review is now included as a published article, adding more outcomes; new comparisons were added; general updates and modifications were made; despite all this, our conclusions remain unchanged.