https://purengom.com/2008/07/07/%ec%a0%9c%ea%b0%80-%eb%b8%94%eb%a1%9c%ea%b7%b8%eb%a5%bc-%ed%95%98%eb%8a%94-%ec%9d%b4%ec%9c%a0-%eb%82%98%eb%a5%bc-%eb%8b%a4%eb%a3%a8%eb%8a%94-%eb%a7%a4%ec%b2%b4%eb%8a%94-%ed%95%98%eb%82%98%ea%b8%b0/