ARC

http://clang.llvm.org/docs/AutomaticReferenceCounting.html#meta

http://longweekendmobile.com/2011/09/07/objc-automatic-reference-counting-in-xcode-explained/

http://www.cocoachina.com/iphonedev/sdk/2011/1121/3552.html

http://www.raywenderlich.com/5677/beginning-arc-in-ios-5-part-1

http://www.learn-cocos2d.com/2011/11/everything-know-about-arc/