anchor.diff:  		(multiple-value-bind (d c)
   		    (do-def domain domain-name class print-name print-label  name)
   		  (cons d c))))
  +            ;; N.B: With regards to normalization of compound unit
  +            ;; expressions, the set of measurement units defined with
  +            ;; this form may be stored in a seperate, constant
  +            ;; (stack allocated) vector of SI base units. The order of
  +            ;; storage of measurement units within that vector will be
  +            ;; significant, and must correspond with section 2.1.2 of 
  +            ;; http://www.bipm.org/en/publications/si-brochure/
  +            ;;
  +            ;; Considering the possibly appolications of an "SI Units"
  +            ;; vector, as such: 
  +            ;; * The "SI Units" vector may be applied for a normal
  +            ;;   ordering of elements within compound unit expressions
  +            ;; * Not only the previous, but the "SI Units" vector may
  +            ;;   also be aplied in normalization of _partially
  +            ;;   normalized_ compound unit expressions (e.g. `W A^-1`)
  +            ;; See also: Documentation, section "Compound unit
  +            ;; expressions" 
   	    '((length "length" meter "metre" "m" :|m|)
   	      (mass "mass" kilogram "kilogram" "kg" :|kg|)
   	      (time "time, duration" second "second" "s" :|s|)
  
positive.code: 
  ;;; %% Angular Measure
  
  (defclass angular-measure (measurement-class)
    ()
    (:metaclass measurement-domain)
    ;; FIXME: #I18N
    (:print-name . "angular measure")
    (:print-label . "angular measure")
    (:symbol . :angular-measure)
    (:base-measure . radian))
  
  (register-measurement-domain (find-class 'angular-measure))
  
  (defclass radian (measurement)
    ()
    (:metaclass angular-measure)
    (:print-name . "radian")
    (:print-label . "rad")
    (:symbol . :|rad|))
  
  (register-measurement-class (find-class 'radian))
  
  ;; (object-print-name (measurement-domain-base-measure (find-class 'angular-measure)))
  ;; => "radian"
  
  (defclass degree (measurement)
    ()
    (:metaclass angular-measure)
    (:base-factor . #.(/ (rational pi) 180) )
    (:print-name . "degree")
    (:print-label . "deg")
  
negative.code:       (md-c (find-class 'measurement-domain))
        (mc-c (find-class 'measurement-class))
        (m-c (find-class 'measurement))
        ;; FIXME: Portable source locations - see also, SLIME/SWANK
        #+SBCL (src (sb-c:source-location)))
    (labels ((do-def (domain domain-name class print-name print-label name)
  	     (let* ((d 
  