<https://www.yamadasaito.com/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.yamadasaito.com/blog/%E9%9B%84%E6%9D%B1%E3%80%80%E7%B4%94%E7%B1%B3%E7%84%A1%E6%BF%BE%E9%81%8E%E7%94%9F%E5%8E%9F%E9%85%92>