https://purengom.com/2008/11/06/%ec%96%b4%eb%a6%b4%ec%a0%81-%ea%b7%b8-%eb%ac%b4%ec%97%87%eb%b3%b4%eb%8b%a4%eb%8f%84-%ec%86%8c%ec%a4%91%ed%96%88%eb%8d%98-%ec%86%8c%eb%a7%9d%ec%9d%84-%eb%8b%b4%ec%95%84-%ed%96%88%eb%8d%98-%ec%95%bd/