<https://ajisai-sano.com/blog/2019/06/09/%e6%98%94%e3%81%aa%e3%81%8c%e3%82%89%e3%81%ae%e3%82%b7%e3%83%b3%e3%83%97%e3%83%ab%e3%82%aa%e3%83%a0%e3%83%a9%e3%82%a4%e3%82%b9/#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://ajisai-sano.com/blog/2019/06/09/%E6%98%94%E3%81%AA%E3%81%8C%E3%82%89%E3%81%AE%E3%82%B7%E3%83%B3%E3%83%97%E3%83%AB%E3%82%AA%E3%83%A0%E3%83%A9%E3%82%A4%E3%82%B9/>