*1:See also https://sumita-m.hatenadiary.com/entry/20080422/1208856877 https://sumita-m.hatenadiary.com/entry/20080619/1213842022 https://sumita-m.hatenadiary.com/entry/20080702/1215017909 https://sumita-m.hatenadiary.com/entry/20161124/1479955493 https://sumita-m.hatenadiary.com/entry/2020/01/14/115748 https://sumita-m.hatenadiary.com/entry/2020/01/29/032304 https://sumita-m.hatenadiary.com/entry/2020/04/07/104850