<http://katsuragawarc.com/programs/3-9%e3%80%8c%e4%bc%91%e4%bc%9a%e3%80%8d/#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://katsuragawarc.com/programs/3-9%E3%80%8C%E4%BC%91%E4%BC%9A%E3%80%8D/>