https://www.syu.ac.kr/doba/2010-2-%eb%b3%b5%ec%88%98%ec%a0%84%ea%b3%b5%eb%b6%80%ec%a0%84%ea%b3%b5-%ec%8b%a0%ec%b2%ad-%ec%9e%90%ea%b2%a9-%eb%b0%8f-%eb%b0%a9%eb%b2%95/