・Slightly modified the wording of the first and final sentences of \S 2.7, (iii)

・Corrected a misprint at the end of \S 2.10 ("labelling apparatuses are being" --->
　"labelling apparatuses as being")

・Corrected a misprint ("functionality" ---> "functoriality") at the end of \S 2.13

・Slightly modified the wording of the first sentence of the second to last item of
　the final display of Example 2.14.3

・Corrected a misprint (a missing "[EtTh]" preceding "Definition 2.13") in the first
　sentence following the fifth display of \S 3.4, (iv)

・Added a supplementary explanatory sentence to the discussion between the
　fourth and fifth displays of \S 3.6, (ii)

・Added a supplementary explanatory sentence to the first item of the final display
　of \S 3.6, (iii)

・Slightly modified the wording of \S 3.7, (ii), (8^{est}) (" "slightly enlarged
　multiradial representation" " ---> "{\it slight enlargement of the multiradial
　representation}")

・Added a supplementary explanation to the final portion of \S 4.4, (i)