<https://www.naokilog.com/2020/04/09/nexus-%e3%82%b7%e3%83%aa%e3%83%bc%e3%82%ba%e3%81%ae%e3%83%8d%e3%83%bc%e3%83%9f%e3%83%b3%e3%82%b0%e8%a6%8f%e5%89%87/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.naokilog.com/2020/04/09/nexus-%E3%82%B7%E3%83%AA%E3%83%BC%E3%82%BA%E3%81%AE%E3%83%8D%E3%83%BC%E3%83%9F%E3%83%B3%E3%82%B0%E8%A6%8F%E5%89%87/>