<https://enjya.net/%e8%a9%b3%e7%b4%b0%e3%83%97%e3%83%a9%e3%83%b3%ef%bc%86%e3%81%8a%e7%94%b3%e8%be%bc%e3%81%bf/#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://enjya.net/%E8%A9%B3%E7%B4%B0%E3%83%97%E3%83%A9%E3%83%B3%EF%BC%86%E3%81%8A%E7%94%B3%E8%BE%BC%E3%81%BF/>