http://high-school.c.u-tokyo.ac.jp/lecture_time/2015A/2015A_11.html

http://headlines.yahoo.co.jp/hl?a=20160128-00050192-yom-soci

http://wpb.shueisha.co.jp/2016/01/27/60035/

https://www.bengo4.com/c_1009/c_22/c_21/n_4222/

http://mainichi.jp/articles/20160129/k00/00m/040/064000c http://www.yomiuri.co.jp/editorial/20160127-OYT1T50095.html