Some authors released free his books

[John3]

Hi, Some books are free, so I think it would be nice, to have some footnote, asterisk by side of the book or something to refers to those books.

Some of I know:

• GPU Gems 1 = https://developer.nvidia.com/gpugems/GPUGems/gpugems_pref01.html
• GPU Gems 2 = https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_inside_front_cover.html
• GPU Gems 3 = https://developer.nvidia.com/gpugems/GPUGems3/gpugems3_pref01.html
• Game AI Pro 1, 2 & 3 = http://www.gameaipro.com/ (* GAIpro3 TBA)
• Game Programming Patterns = http://gameprogrammingpatterns.com/contents.html
• Invent Your Own Computer Games with Python = http://inventwithpython.com/chapters/
• Making Games with Python and Pygame = http://inventwithpython.com/pygame/chapters/
• OpenGL Insights = http://openglinsights.com/cover.html
• Structure and Interpretation of Computer Programs = https://mitpress.mit.edu/sites/default/files/sicp/full-text/book/book.html
• ShaderX 1 & 2 = http://www.realtimerendering.com/resources/shaderx/

Edit: Update links