http://help.adobe.com/en_US/ActionScript/3.0_ProgrammingAS3/WS5b3ccc516d4fbf351e63e3d118a9b90204-7ec0.html
AS3 101: OOP Introduction – Basix
http://code.tutsplus.com/tutorials/as3-101-oop-introduction-basix--active-5789