<https://gionkonishi.com/2020/07/11/%e5%90%89%e6%9d%91%e6%95%8f%e6%b2%bb/#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://gionkonishi.com/2020/07/11/%E5%90%89%E6%9D%91%E6%95%8F%E6%B2%BB/>