grading system of guidelines

In WCAG is present a system for grading guideline recommendations? i
dont understand foundation and research works maybe used not cited. Is
available a document of explanations for grading system, if exist? or
simply on scientific basis of WCAG?
	
thanks
Livio Mondini

<example: http://www.bmj.com/cgi/content/full/323/7308/334>

Received on Thursday, 9 November 2006 06:26:45 UTC