http://www.utp.or.jp/topics/files/2015/up510.pdf

http://headlines.yahoo.co.jp/hl?a=20150413-00000064-mai-soci

http://news.goo.ne.jp/article/yomiuri/nation/20150413-567-OYT1T50020.html

http://news.livedoor.com/article/detail/10001838/

http://www3.nhk.or.jp/news/html/20150412/k10010045311000.html