https://www.syu.ac.kr/blog/%eb%b3%b4%eb%8f%84%ec%9e%90%eb%a3%8c-%ec%82%bc%ec%9c%a1%eb%8c%80-%ec%b0%bd%ec%97%85%ec%ba%a0%ed%94%84-%ea%b0%9c%ec%b5%9c-%ec%b0%bd%ec%97%85-%ec%83%88%ec%8b%b9%eb%93%a4-%eb%aa%a8%ec%97%ac/%ec%82%ac%ec%a7%84-%ec%82%bc%ec%9c%a1%eb%8c%80-%ec%b0%bd%ec%97%85%ec%ba%a0%ed%94%84-2/