URLDate
Verified		Extra Software
Requirements
(if any)		Access
Conditions		Notes
http://dx.doi.org/10.1136/bjsm.2007.037267DOI Link
http://bjsm.bmj.com/content/41/suppl_1/i20.full10/16/2014Item is within a limited-access website
http://bjsm.bmj.com/content/41/suppl_1/i20.full.pdf10/16/2014PDF ReaderItem is within a limited-access website