*1:See also https://sumita-m.hatenadiary.com/entry/20100318/1268931002 https://sumita-m.hatenadiary.com/entry/20160406/1459870653 https://sumita-m.hatenadiary.com/entry/20160919/1474255091 https://sumita-m.hatenadiary.com/entry/20170420/1492710355 https://sumita-m.hatenadiary.com/entry/2020/06/01/145035