<https://www.programing-tips.com/blog/2021/08/29/%e3%80%90css%e5%85%a5%e9%96%80%e3%80%91%e3%83%86%e3%82%ad%e3%82%b9%e3%83%88%e3%82%92%e8%a3%85%e9%a3%be%e3%81%99%e3%82%8b%e3%83%97%e3%83%ad%e3%83%91%e3%83%86%e3%82%a3%e3%82%92%e5%ad%a6%e3%81%bc/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.programing-tips.com/blog/2021/08/29/%E3%80%90css%E5%85%A5%E9%96%80%E3%80%91%E3%83%86%E3%82%AD%E3%82%B9%E3%83%88%E3%82%92%E8%A3%85%E9%A3%BE%E3%81%99%E3%82%8B%E3%83%97%E3%83%AD%E3%83%91%E3%83%86%E3%82%A3%E3%82%92%E5%AD%A6%E3%81%BC/>