Jähnichen, Jan Sürmeli.(2017).Self-sovereign Identity − Opportunities and Challenges for the Digital Revolution.from https://arxiv.org/abs/1712.01767 http://www.projectliberty.org/ https://internet.watch.impress.co.jp/www/article/2003/0416/liberty.htm https://www.okta.com/identity-101/federated-identity-vs-sso/ by @kota_yata