https://www.syu.ac.kr/blog/2018-2%ed%95%99%ea%b8%b0-%ea%b3%84%ec%a0%88-%ea%b5%90%ec%96%91%ec%84%a0%ed%83%9d-%ed%86%a0%ec%9d%b5-i-ii-%ec%98%a8%eb%9d%bc%ec%9d%b8-%ec%88%98%ec%97%85-%ec%95%88%eb%82%b4/%ec%8a%a4%eb%af%b8%ec%8a%a4%ea%b5%90%ec%96%91%eb%8c%80%ed%95%99-2/