*1:See also https://sumita-m.hatenadiary.com/entry/20080523/1211561175 https://sumita-m.hatenadiary.com/entry/20150724/1437745163 https://sumita-m.hatenadiary.com/entry/20170324/1490328369 https://sumita-m.hatenadiary.com/entry/2019/04/02/012302 https://sumita-m.hatenadiary.com/entry/2020/02/20/022728
