*1:See also https://sumita-m.hatenadiary.com/entry/20130409/1365532728 https://sumita-m.hatenadiary.com/entry/20130417/1366211836 https://sumita-m.hatenadiary.com/entry/20140824/1408844676 https://sumita-m.hatenadiary.com/entry/2021/01/20/005129 https://sumita-m.hatenadiary.com/entry/2021/03/03/003829