DOCBOOK: I need a suggestion on how to mark up references to notes.

I'm working on a publication using docbook.  We have a lot of additional
notes that I'd like to reference from within the book, but am unsure as
to what the best way to mark them up is.

Here's a fragment from the book to show what I mean:

    <para> 1. The paths shown here are circular and simply connected.
    What happens if the paths are not circular? In note 144 I deal with
    the non circular paths using line integrals and the Residue theorem.
    However I can leave my paths circular without loosing generality
    for several reasons. </para>

What's the best way to mark up note 144?
So far I've come up with:
* I could define a new element and write my own DSSSL to handle it.
* Perhaps I could treat all the notes like a bibliography, and instead
  cite them.

Has anyone got any experience or suggestions that they can make me?
I'd be very grateful.

Thanks,
Joe