https://www.hokkaido-np.co.jp/article/157260

http://www.sankei.com/affairs/news/180116/afr1801160037-n1.html

https://www3.nhk.or.jp/news/html/20180116/k10011290101000.html

https://www3.nhk.or.jp/news/html/20180117/k10011291411000.html

https://www.westlawjapan.com/p_affairs/2018/20180116_s.html