*1:See also https://sumita-m.hatenadiary.com/entry/20101221/1292912515 https://sumita-m.hatenadiary.com/entry/20150730/1438223216 https://sumita-m.hatenadiary.com/entry/2020/12/23/133417 https://sumita-m.hatenadiary.com/entry/2020/12/27/101709 https://sumita-m.hatenadiary.com/entry/2021/01/03/030914 https://sumita-m.hatenadiary.com/entry/2021/02/06/185051 https://sumita-m.hatenadiary.com/entry/2021/03/30/081149