https://www.syu.ac.kr/cass/2020/06/30/2020-1-%ec%bd%94%eb%a1%9c%eb%82%98-%eb%b0%94%ec%9d%b4%eb%9f%ac%ec%8a%a4-%ec%98%88%eb%b0%a9-%ec%ba%a0%ed%8e%98%ec%9d%b8-%ea%b3%b5%eb%aa%a8%ec%a0%84-%ec%88%98%ec%83%81%ec%9e%916-2/