<https://haru-michiko.com/%e3%83%aa%e3%83%8f%e3%83%93%e3%83%aa%e3%81%9d%e3%81%ae%e5%be%8c-2/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://haru-michiko.com/%E3%83%AA%E3%83%8F%E3%83%93%E3%83%AA%E3%81%9D%E3%81%AE%E5%BE%8C-2/>