<https://www.hitotsuyoga.com/post/2016/07/20/7\u6708\u306E\u6E80\u6708\u306B>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.hitotsuyoga.com/post/2016/07/20/7%E6%9C%88%E3%81%AE%E6%BA%80%E6%9C%88%E3%81%AB>