https://www.syu.ac.kr/blog/%eb%b0%a9%ed%95%99-%ec%a4%91%ec%97%90%eb%8f%84-%eb%8c%80%ed%95%99%ec%9d%bc%ec%9e%90%eb%a6%ac%ec%84%bc%ed%84%b0%ec%9d%98-%ec%a7%84%eb%a1%9c-%eb%b0%8f-%ec%b7%a8%ec%97%85%ec%83%81%eb%8b%b4%ec%9d%80/%ec%83%81%eb%8b%b4-%ed%99%8d%eb%b3%b4-pdf_page_1/