https://headlines.yahoo.co.jp/hl?a=20170502-00000015-mai-soci

https://mainichi.jp/articles/20170502/k00/00e/040/231000c

http://blog.livedoor.jp/schulze/archives/52186107.html

http://blogos.com/article/220989/

http://business.nikkeibp.co.jp/atcl/report/15/120100058/042700013/