<https://www.kurabuchi-eigomura.jp/blog/winter-course-2%e6%97%a5%e7%9b%ae/#breadcrumblist>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.kurabuchi-eigomura.jp/blog/winter-course-2%E6%97%A5%E7%9B%AE/>