https://purengom.com/2011/06/02/iphoneipad-%eb%8d%b0%ec%9d%b4%ed%84%b0-%eb%b0%b1%ec%97%85%ec%9d%84-%ec%95%94%ed%98%b8%ed%99%94-%ed%95%b4%ec%95%bc-%ed%95%98%eb%8a%94-%ea%b9%8c%eb%8b%ad/