1.http://www.kirupa.com/developer/actionscript/isometric_transforms2.htm
2.http://www.gamedev.net/page/resources/_/technical/game-programming/isometric-n-hexagonal-maps-part-i-r747
3.http://stackoverflow.com/questions/892811/drawing-isometric-game-worlds
4.http://fivedots.coe.psu.ac.th/~ad/jg/ch064/index.html