https://rein.kr/posts/2011-05-30-ndc-%EC%B0%B8%EA%B4%80%EA%B8%B0-%EB%A9%94%EC%9D%B4%ED%94%8C%EC%8A%A4%ED%86%A0%EB%A6%AC-%EA%B0%9C%EB%B0%9C%EC%8A%A4%ED%86%A0%EB%A6%AC-%EB%8D%94-%EC%9E%98%EB%90%98%EB%8A%94-%EA%B2%8C%EC%9E%84/