https://purengom.com/2008/02/12/%eb%8f%84%eb%8c%80%ec%b2%b4-%ed%95%9c%ea%b5%ad%ec%97%90%eb%8a%94-%ec%99%9c-%ec%97%86%eb%8a%94%ea%b1%b0%ec%a7%80-%ec%8b%9c%eb%a6%ac%ec%a6%88-1-%eb%94%94%ec%a7%80%ed%84%b8-%eb%b9%84%eb%94%94%ec%98%a4/