https://www.syu.ac.kr/blog/%ec%8b%9c%eb%a6%bd%ec%84%b1%eb%8f%99%ec%b2%ad%ec%86%8c%eb%85%84%ec%84%bc%ed%84%b0-%ec%a7%81%ec%9b%90-%ec%b1%84%ec%9a%a9%ea%b3%b5%ea%b3%a0-2/%ec%a7%81%ec%9b%90-%ec%b1%84%ec%9a%a9-%ea%b3%b5%ea%b3%a0%ec%9c%a1%ec%95%84%eb%8c%80%ec%b2%b4%ec%9d%b8%eb%a0%a5-pdf_page_1/