anchor.diff:    ()
     (:report
      (lambda (c s)
  -     (format s "No measureent prefix registered for name ~S"
  +     (format s "No measurement prefix registered for name ~S"
                (entity-not-found-name c)))))
   
   (define-condition prefix-degree-not-found (entity-not-found)
     ()
     (:report
      (lambda (c s)
  -     (format s "No measureent prefix registered for degree ~S"
  +     (format s "No measurement prefix registered for degree ~S"
                (entity-not-found-name c)))))
   
   
  
positive.code: 
  (deftype prefix-degree ()
    '(and (integer -24 24)
      (member 0 
       1 2 3 6 9 12 15 18 21 24
       -1 -2 -3 -6 -9 -12 -15 -18 -21 -24)))
  
negative.code:   (rescale scalar (prefix-degree prefix)))
  
  
  (defmethod nrescale ((scalar measurement) (prefix fixnum))
    (multiple-value-bind (new-mag new-deg) 
        (shift-magnitude (measurement-magnitude scalar)
  