<https://heiseikai.org/blog/2015/03/25/%e7%b7%8f%e5%90%88%e7%81%ab%e7%81%bd%e9%81%bf%e9%9b%a3%e8%a8%93%e7%b7%b4-2/#primaryimage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://heiseikai.org/blog/2015/03/25/%E7%B7%8F%E5%90%88%E7%81%AB%E7%81%BD%E9%81%BF%E9%9B%A3%E8%A8%93%E7%B7%B4-2/>