https://purengom.com/2010/08/22/%ec%9a%94%ec%a6%98-%ec%a0%9c%ea%b0%80-%ec%97%b4%ec%a4%91%ed%95%98%ea%b3%a0-%ec%9e%88%eb%8a%94%ea%b2%83%ec%9d%b4-%ec%9e%88%ec%8a%b5%eb%8b%88%eb%8b%a4-mac-wiki/