http://www.afpbb.com/articles/-/2964374?pid=11252905

http://japanese.ruvr.ru/2013_10_04/122381615/

http://news.ameba.jp/20131012-202/

http://jp.sciencenewsline.com/articles/2013100815010013.html

http://diamond.jp/articles/-/42652

http://news.goo.ne.jp/article/kahoku/nation/kahoku_K201310130A0EA0XX00006_214911.html