https://www.syu.ac.kr/blog/%ec%b4%9d%eb%8f%99%eb%ac%b8%ed%9a%8c%ec%9e%a5-%ec%9e%84%ec%a2%85%ec%84%b1-%ed%99%94%eb%b0%b1-%ec%9e%a5%ed%95%99%ea%b8%b0%ea%b8%88-%eb%a7%88%eb%a0%a8-%ec%b4%88%eb%8c%80%ec%a0%84/%ec%82%ac%ec%a7%84-%ec%9e%84%ec%a2%85%ec%84%b1-%ed%99%94%eb%b0%b1-1/