https://purengom.com/2008/02/19/%ed%94%8c%eb%9d%bc%ec%a6%88%eb%a7%88-%eb%94%94%ec%8a%a4%ed%94%8c%eb%a0%88%ec%9d%b4-%ed%8c%a8%eb%84%90-%ec%84%9c%ec%9e%90%ea%b0%80-%eb%90%98%ec%96%b4%eb%b2%84%eb%a6%b0-%eb%b9%84%ec%9a%b4%ec%9d%98/