Message
xref
has @ref-type="author-notes" but does not point to an <fn/> element in an <author-notes/>
element.
Rule XPath:
This rule REPORTS an alert when the following is TRUE:
@ref-type = 'author-notes' and not(every $rid in tokenize(@rid, '\s+') satisfies key('element-by-id',
$rid)[self::fn/parent::author-notes])