Suggest books or resources on shaders in OpenGL ES

Question

Java

Please suggest some good book on OpenGL Shaders in Java for Android.
Good sites on the topic will also do.
I would like to figure out how they still work, especially pixel shaders.

Answer 1

The OpenGL® ES Shading Language
GLSL_ES_Specification_3.00.3
OpenGL. 3D Graphics and Shader Programming Language
Wolff D. - OpenGL 4.0 Shading Language Cookbook - 2011.pdf