CSS Pre-Processors: Stylus, Less & Sass - Speaker Deck
Expressive, dynamic, robust CSS - ppt download
An Introduction to CSS Pre-Processors: SASS, LESS and Stylus | by Madhavan Nagarajan | Medium
Axis
Stir up Your Own Delicious Sass Mixins
What is the best method for adding 2x images to webpages that will be displayed on the new iPad with Retina graphics? What's the best way to handle 2x sprites? - Quora