<https://nori2.jp/2007/02/12/%e3%82%b6%e3%83%b3%e3%82%b8%e3%83%90%e3%83%ab%e3%81%ae%e5%a5%b3%e5%b0%86/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://nori2.jp/2007/02/12/%E3%82%B6%E3%83%B3%E3%82%B8%E3%83%90%E3%83%AB%E3%81%AE%E5%A5%B3%E5%B0%86/>