... continued ...

although I found a strange bug in the tangling and noweb syntax.  I
didn't want to have quotes in the text so I removed them and put them in
the lisp src block instead:

#+begin_src org
  ,#+NAME: ADD
  ,#+BEGIN_SRC emacs-lisp -n -r :noweb yes :tangle test.el

  (defun add (x y)
    "<<DOC-OF-ADD>>" ;; code to code
    (+ x y) (ref:add)
    )
  ,#+END_SRC
#+end_src

which when exported or tangled resulted in some strange quoting:

#+begin_src emacs-lisp
  (defun add (x y)
    "
    "We use the function add to calculate the sum of two numbers." ;; code to code
    (+ x y) 
    )
#+end_src

I'm probably not supposed to put a <<...>> link within quotes but the
output is surprising in any case.

-- 
Eric S Fraga via Emacs 27.0.50, Org release_9.1.6-591-gee336b