(canonical reference) specifies the destination of the pointer by supplying a canonical reference from a
scheme defined in a refsDecl element in the TEI header
the value of cRef should be constructed so
that when the algorithm for the resolution of canonical
references (described in section 16.2.5 Canonical References) is
applied to it the result is a valid URI reference to the
intended target
Note
The refsDecl to use may be indicated with the decls attribute.
Currently these Guidelines only provide for a single canonical reference to be encoded on
any given ptr element.