https://rein.kr/posts/2012-05-02-ndc-%EC%B0%B8%EA%B4%80%EA%B8%B0-%EB%8D%A4%ED%94%84-%ED%8C%8C%EC%9D%BC%EC%9D%84-%ED%86%B5%ED%95%9C-%EC%82%AC%ED%9B%84-%EB%94%94%EB%B2%84%EA%B9%85-%EC%8B%A4%EC%9A%A9-%ED%85%8C%ED%81%AC%EB%8B%89/