*1:See also https://sumita-m.hatenadiary.com/entry/20130607/1370563792 https://sumita-m.hatenadiary.com/entry/20150612/1434075474 https://sumita-m.hatenadiary.com/entry/20160824/1472005939 https://sumita-m.hatenadiary.com/entry/2020/02/12/020430 https://sumita-m.hatenadiary.com/entry/2020/06/24/193511