https://mainichi.jp/articles/20180321/k00/00m/040/191000c
https://www.nikkansports.com/m/olympic/pyeongchang2018/speedskate/news/201802240000789_m.html?mode=all
https://www.google.com/amp/www.sankei.com/economy/amp/180321/ecn1803210036-a.html#ampshare=http://www.sankei.com/economy/news/180321/ecn1803210036-n1.html
http://jp.wsj.com/articles/SB12386457582361034431504584112352170335422
http://www.itmedia.co.jp/news/spv/1803/20/news050.html