*1:See also https://sumita-m.hatenadiary.com/entry/2021/03/27/074834 https://sumita-m.hatenadiary.com/entry/2021/03/29/211943 https://sumita-m.hatenadiary.com/entry/2021/04/03/021130
*2:See also https://sumita-m.hatenadiary.com/entry/20100803/1280799813 https://sumita-m.hatenadiary.com/entry/2021/04/05/024906