(2021-04-15) ・Added an Introduction ・In \S 1.3, added "(UndIg)", as well as a reference to "(Undig)" in \S 2.1 ・Rewrote various portions of \S 1.5 ・Rewrote Example 2.4.4 ・Modified the title of Example 2.4.5 ・Added Example 2.4.6 ・Slightly modified the paragraph at the beginning of \S 3 ・Slightly modified the final portion of \S 3.1 concerning (FxRng), (FxEuc), (FxFld) ・Added Example 3.9.1 and made slight modifications to the surrounding text ・In \S 3.10, rewrote the discussion preceding (Stp1) ・In \S 3.11, slightly modified the discussion following ({\Theta}ORInd) (2021-04-18) ・Added item (iv) to Example 2.4.6 ・Made slight modifications to (AND(XOR)-Chn1) and (AND(XOR)-Chn2) in \S 3.10 (2021-04-25) ・Slightly modified the final portions of (Stp7), (Stp8) ・Slightly modified the text immediately following (DltLb) (2021-05-27) ・Slightly modified the Introduction ・In \S 1.3, \S 1.8, added references to Example 2.4.5 ・In \S 1.5, added a reference to \S 1.10 ・Added \S 1.10 ・Added items (iv), (v), (vi), (vii), (viii) to Example 2.4.5 ・Rewrote the introductory portion of Example 3.5.2 ・In \S 3.6, slightly modified (Syp2) ・Slightly modified the discussion of "numerous classical constructions" at the end of \S 3.8 ・Slightly modified the discussion surrounding Example 3.9.1 ・In \S 3.10, slightly modified the discussion of (Stp1), (Stp2), (Stp3), (Stp7), (Stp8) ・At the end of \S 3.10, added a supplementary explanation of the term "closed loop" ・In \S 3.11, corrected a slight inaccuracy in the wording of (Ind3>1+2) ・In \S 3.11, added a paragraph concerning the qualitative similarity of (ExtInd2) to (logORInd), ($\Theta$ORInd) ・Slightly modified the discussion surrounding (RcnLb) in \S 3.11 (2021-06-04) ・In \S 1.10, slightly modified the wording of (Pyth4) ・Added a supplementary explanation to the discussion of crystals in \S 3.5 ・Added item (v) to Exmaple 3.5.2 ・Slightly modified the wording of (AND(XOR)-Chn1) in \S 3.10