<https://j-credo.com/#website>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://j-credo.com/letter/%E3%82%AF%E3%83%AC%E3%83%89%E3%82%92%E8%B6%85%E3%81%88%E3%82%8B%E4%BA%BA%E6%9D%90%E3%81%AF%E8%82%B2%E3%81%9F%E3%81%AA%E3%81%84/>