As I didn´t find it in the list, here is THE article about premultiplied alpha: https://developer.nvidia.com/content/alpha-blending-pre-or-not-pre

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com