(2021-01-15)

・Slightly modified the statement of Theorems A, B, and F

・Slightly modified the statement of Corollary 6.5, (iii), as well as the
　discussion of Corollary 6.5, (iii), in the Introduction

(2022-12-30)

・Slightly modified the first display in the third paragraph
　following Theorem C

・Added a reference to [NCBel] in the proof of Theorem 4.4

・Added two entries ([Belyi], [NCBel]) to the Bibliography

・Updated the bibliographical data for [CbTpII], [Hsh2], [HMM]