http://www.sitepoint.com/build-css-preprocessor-postcss/
https://blog.logentries.com/2014/10/which-css-preprocessor-should-you-choose/
http://blog.teamtreehouse.com/how-to-choose-the-right-css-preprocessor
https://www.urbaninsight.com/2012/04/12/ten-reasons-you-should-be-using-css-preprocessor
http://www.sitepoint.com/6-current-options-css-preprocessors
http://css-tricks.com/musings-on-preprocessing/
http://www.catswhocode.com/blog/8-css-preprocessors-to-speed-up-development-time
http://www.youtube.com/watch?v=OXpCB3U_4Ig
http://yui.github.com/yuicompressor/css.html
http://code.google.com/p/closure-stylesheets/
http://www.sitepoint.com/getting-started-myth-preprocessor-future/
What are the features supported by CSS preprocessors?
The first major CSS preprocessor was Sass, released in 2006. It featured a new concise syntax (indentation instead of brackets, no semicolons, etc.) and added advanced features missing from CSS, such as variables, helper functions, and calculations.
