DOCBOOK-APPS: Reference element and chapter numbering

[Vladimir Ivanovic <ivanovic at parc dot xerox dot com>]

I replaced Appendix A  with a Reference. Now my chapters are numbered 1,
2, 3, I, A  whereas they were formerly numbered 1, 2, 3, A, B.

I could live with 1, 2, 3, 4, A, but where does "I" come from? I've
never seen roman numerals as chapter-like numbers in a book when arabic
numerals exist. 

To "fix" this, I tried using

  (define (component-number-sibling-list cmp)
    ;; Return the list of elements with which 'cmp' should be numbered.
    ;; For example, for PART it might return '("PART" "REFERENCE") causing
    ;; sibling parts and references to be numbered together.
    (let ((name (gi cmp)))
      (cond
       ((equal? name (normalize "set"))       (set-number-sibling-list cmp))
       ((equal? name (normalize "book"))      (book-number-sibling-list cmp))
       ((equal? name (normalize "part"))      (part-number-sibling-list cmp))
       ((equal? name (normalize "reference")) (chapter-number-sibling-list cmp))
       ((equal? name (normalize "preface"))   (preface-number-sibling-list cmp))
       ((equal? name (normalize "chapter"))   (chapter-number-sibling-list cmp))
       ((equal? name (normalize "appendix"))  (appendix-number-sibling-list cmp))
       ((equal? name (normalize "article"))   (article-number-sibling-list cmp))
       ((equal? name (normalize "glossary"))  (glossary-number-sibling-list cmp))
       ((equal? name (normalize "bibliography")) (bibliography-number-sibling-list cmp))
       ((equal? name (normalize "index"))     (index-number-sibling-list cmp))
       ((equal? name (normalize "setindex"))  (setindex-number-sibling-list cmp))
       ((equal? name (normalize "refentry"))  (refentry-number-sibling-list cmp))
       (else (default-number-sibling-list cmp)))))

in my own DSSSL driver to get references to be numbered along with
chapters, but it doesn't seem to have any effect.

Any ideas?

-- Vladimir