<https://www.dailynk.com/%ed%95%9c-%60%e6%96%b0%eb%8c%80%eb%b6%81%ec%a0%95%ec%b1%85-%eb%85%bc%eb%9e%80-%ea%b3%84%ec%86%8d/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.dailynk.com/%ED%95%9C-%60%E6%96%B0%EB%8C%80%EB%B6%81%EC%A0%95%EC%B1%85-%EB%85%BC%EB%9E%80-%EA%B3%84%EC%86%8D/>