◊(Local Yarn Code "Diff")

                [url (or (hash-ref link-urls url-ref #f)
                         (format "Missing reference: ~a" url-ref))])
           `(a [[href ,url]] ,@(get-elements tx)))]
        [else tx]))

;; Quick link to another article
(define (html-xref . elems)
  `(a [[href ,(format "~aarticles/~a.html" web-root (first elems))]
       [class "xref"]]
      ,@(rest elems)))
;; Fast link to another article
(define html-xref
  (case-lambda
    [(title) `(a [[href ,(format "~aarticles/~a.html" web-root (normalize title))]
                  [class "xref"]]
                 (i ,title))]
    [elems `(a [[href ,(format "~aarticles/~a.html" web-root (first elems))]
                [class "xref"]]
               ,@(rest elems))]))

;; Footnotes
;;
;; Private use:
(define fn-names null)