<https://haracyu.com/2020/04/30/%e3%83%a2%e3%83%87%e3%83%aa%e3%83%b3%e3%82%b0%e3%81%a8%e7%8f%be%e5%a0%b4/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://haracyu.com/2020/04/30/%E3%83%A2%E3%83%87%E3%83%AA%E3%83%B3%E3%82%B0%E3%81%A8%E7%8F%BE%E5%A0%B4/>