・Slightly reworded the discussion of "IPL" in the first display of Remark 3.11.1, (iii) ・Slightly reworded the discussion of "output data" in the first display of Remark 3.11.1, (v) ・Introduced the notation "R" in the discussion immediately following the first display of Remark 3.11.1, (vi),  and also in the final display of Remark 3.11.1, (vi) ・Corrected a misprint in the second sentence of Remark 3.11.1, (vii) ("one the following" ---> "one of the following") ・Slightly modified the discussion of the "two approaches" in Remark 3.11.1, (vii)