https://www.syu.ac.kr/blog/2021%eb%85%84-%ec%a0%9c4%ec%b0%a8-%ec%9e%ac%eb%8b%a8%eb%b2%95%ec%9d%b8-%ec%84%b8%ec%a2%85%ed%8a%b9%eb%b3%84%ec%9e%90%ec%b9%98%ec%8b%9c-%ec%82%ac%ed%9a%8c%ec%84%9c%eb%b9%84%ec%8a%a4%ec%9b%90-%eb%b3%b8/%eb%b3%84%ec%a7%801%ec%97%b0%ea%b5%ac%ec%a7%81-3%ea%b8%89-%ec%97%b0%ea%b5%ac%ec%8b%a4%ec%a0%81-%eb%aa%a9%eb%a1%9d-%ec%96%91%ec%8b%9d/