Make a link to code in another document. There is no defined semantics attached to this link in general, but it might be used to document a dependency between two modules, such as a source code file depending on an include file.
The document referred to should be marked up using this programcode DTD.
As with the codegroup element, the DSSSL DTD adds
semantics to this element. It maps this element to the
external-specification element in the DSSSL architecture.
(docblock)
codereference |_(docblock)
An ID within the target document, if required.
A subdoc entity which references the document being linked to.