*1:See also https://sumita-m.hatenadiary.com/entry/2019/11/15/030331
*2:See also https://sumita-m.hatenadiary.com/entry/20150730/1438223216 https://sumita-m.hatenadiary.com/entry/20160901/1472698103 https://sumita-m.hatenadiary.com/entry/20170321/1490117707 https://sumita-m.hatenadiary.com/entry/2020/01/01/123253 https://sumita-m.hatenadiary.com/entry/2020/01/18/130200