*1:See also https://sumita-m.hatenadiary.com/entry/20100729/1280429288 https://sumita-m.hatenadiary.com/entry/20101229/1293610997 https://sumita-m.hatenadiary.com/entry/20130614/1371221716 https://sumita-m.hatenadiary.com/entry/20140728/1406522463 https://sumita-m.hatenadiary.com/entry/2019/01/26/235846 https://sumita-m.hatenadiary.com/entry/2020/02/03/234710 https://sumita-m.hatenadiary.com/entry/2020/02/05/012724