Tài liệu tham khảo WikiPedia: IOS 9 http://arstechnica.com/apple/2015/09/apple-ios-9-o... http://www.cnet.com/news/apple-touts-ios-9-adoptio... http://ios9guide.com/top-10-featuress-why-ios-9-is... http://mymobotips.com/how-to-improve-ios-9-battery... https://developer.apple.com/support/app-store/ https://support.apple.com/kb/dl1842?locale=en_US https://www.apple.com/ios/ https://web.archive.org/web/20160906075542/https:/...
