Name
reference — Describes an external document
Content model
reference :  xmlns:xlink,  xlink:type,  refID,  author,  title,  [accession],  date,  [xlink:href]
     EMPTY
Attributes
| xmlns:xlink | 
| xlink:type | 
| refID - an internal, document-unique, XML identifier for this reference definition | 
| author - the name of the author of the reference | 
| title - the title of the referenced document | 
| accession (optional) - the accession number (ISBN or organization report number) of the document | 
| date - the date of the document, in YYYY-MM-DD format | 
| xlink:href (optional) - an optional URL to an on-line copy of the document | 
Description
A reference element associates an external document with an ID  
 making use of XLink semantics.