http://yama-ben.cocolog-nifty.com/ooinikataru/20170331kougisho.pdf

http://gendai.ismedia.jp/articles/-/51347

http://jila.jp/pdf/questionnaire201702.pdf

https://headlines.yahoo.co.jp/hl?a=20170331-00000011-ryu-oki

http://www.nikkei.com/article/DGXLASFS28H3A_Q7A330C1EA1000/