https://purengom.com/2009/09/12/%ec%a0%81%ea%b7%b9%ec%a0%81%ec%9d%b8-%eb%94%94%ec%a7%80%ed%84%b8-%ed%85%94%eb%a0%88%eb%b9%84%ec%a0%84-%ec%a0%84%ed%99%98-%ec%95%88%eb%82%b4%ea%b0%80-%ec%8b%9c%ea%b8%89%ed%95%98%eb%8b%a4/