<https://chiya-eng.com/2018/11/18/no-study-gram/%e4%b8%80%e4%ba%ba%e6%9a%ae%e3%82%89%e3%81%97%e5%af%82%e3%81%97%e3%81%84%e5%bd%bc%e6%b0%8f%e6%ac%b2%e3%81%97%e3%81%8410/#listItem>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://chiya-eng.com/2018/11/18/no-study-gram/%E4%B8%80%E4%BA%BA%E6%9A%AE%E3%82%89%E3%81%97%E5%AF%82%E3%81%97%E3%81%84%E5%BD%BC%E6%B0%8F%E6%AC%B2%E3%81%97%E3%81%8410/>