<https://hsinjung.blog/4925/2018-07-17-%e8%a8%ba%e9%96%93%e9%80%9f%e5%af%ab/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://hsinjung.blog/4925/2018-07-17-%E8%A8%BA%E9%96%93%E9%80%9F%E5%AF%AB/>