<https://nihongo-learn.com/%e5%a4%9a%e7%9b%8a%e8%aa%b2%e7%a8%8b/toeic%e5%a4%9a%e7%9b%8a%e8%80%83%e8%a9%a6/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://nihongo-learn.com/%E5%A4%9A%E7%9B%8A%E8%AA%B2%E7%A8%8B/toeic%E5%A4%9A%E7%9B%8A%E8%80%83%E8%A9%A6/>