<https://www.boost-web.com/tag/%e8%a1%9d%e5%8b%95%e8%b2%b7%e3%81%84#collectionpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.boost-web.com/tag/%E8%A1%9D%E5%8B%95%E8%B2%B7%E3%81%84>