*1:See also https://sumita-m.hatenadiary.com/entry/20091228/1262008004 https://sumita-m.hatenadiary.com/entry/20070329/1175189030 https://sumita-m.hatenadiary.com/entry/20140724/1406181296 https://sumita-m.hatenadiary.com/entry/20160307/1457362338 https://sumita-m.hatenadiary.com/entry/2020/01/07/134037