*1:See also https://sumita-m.hatenadiary.com/entry/20080924/1222232183 https://sumita-m.hatenadiary.com/entry/20090526/1243310323 https://sumita-m.hatenadiary.com/entry/20170420/1492710355 https://sumita-m.hatenadiary.com/entry/20181018/1539881036 https://sumita-m.hatenadiary.com/entry/2019/11/26/012021