https://purengom.com/2008/06/29/%eb%8b%b9%ec%8b%a0%eb%93%a4%ec%9d%80-%eb%8d%94-%eb%9b%b0%ec%a7%80-%ec%95%8a%ec%95%84%eb%8f%84-%eb%90%a9%eb%8b%88%eb%8b%a4-%ec%82%bc%ec%84%b1-%ea%b8%b0%ec%97%85-%ea%b4%91%ea%b3%a0%ec%97%90-%eb%8c%80/