https://purengom.com/2008/06/13/%ec%9d%bc%eb%b3%b8-%eb%93%9c%eb%9d%bc%eb%a7%88-%ec%b2%b4%ec%9d%b8%ec%a7%80change-%ec%a4%91-%ec%9d%b4%eb%aa%85%eb%b0%95%ec%9d%80-%ec%83%88%ea%b2%a8-%eb%93%a4%ec%9c%bc%ec%8b%9c%eb%9d%bc/