National Review:
http://www.nationalreview.com/corner/265767/pdf-layers-obamas-birth-certificate-nathan-goulding
Youtube Demo of how layers are created by adobe:
http://www.youtube.com/watch?v=XcWQw2AAIho
The National Review explanation was just painfully and obviously stupid. The video demo was rather poor and lacked the obvious expertise that the demos linked in post #47 has.