The attributes key and ref, inherited from the class att.canonical may be used to indicate the canonical form for the title; the former, by supplying
(for example) the identifier of a record in some external library system; the latter
by pointing to an XML element somewhere containing the canonical form of the title.
예
<title>Information Technology and the Research Process: Proceedings of a conference held at Cranfield Institute of Technology, UK, 18–21 July 1989</title>
<title type="full"> <title type="main">Synthèse</title> <title type="sub">an international journal for epistemology, methodology and history of science</title> </title>