<https://erikahadama.pixnet.net/blog/post/357329042-%e3%80%90%e5%8f%b0%e4%b8%ad%e7%b4%8b%e5%94%87%e3%80%91double-q%e5%98%9f%e5%98%9f%e5%94%87%e5%b1%95%e7%8f%be%e6%b0%b4%e6%84%9f%e5%85%89%e6%be%a4%e2%80%bb%e5%88%a5>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://erikahadama.pixnet.net/blog/post/357329042>