documentRef
documentRef — Reference to an external document
Content model
documentRef :  [docID],  refID
     EMPTYAttributes
- 
docID
 (optional) 
			(deprecated)
		      The internal identifier of a reference definition element.
- 
refID
 The internal identifier of a reference definition element.
Future plans for this element
      The 'docID' attribute is deprecated; it has been renamed 'refID'
      to match its use in the 'reference' element. This attribute
      will be removed in a future version of DAVE-ML.