1. 1) Public Works Research Institute, (2017): Report by Investigation Committee on Road Collapse at Construction Site of Subway Tunnel for Extension of Nanakuma Line, Fukuoka, https://www.pwri.go.jp/jpn/kentou-iinkai/kentou-iinkai.html (written in Japanese)
2. 2) Yuri A., (2016): There are those who are more vicious than Asahi-Kasei, Bungeishunnju, 2016(1), 158-167 (written in Japanese)