The master guide to smooth, realistic shadows in CSS - DEV Community
LESS CSS Pre-processor
Bootstrap on Twitter: "We'll be bringing CSS variables to more components in each minor v5 release to make customization easier and even reduce file size in some cases. Consider this before and
The master guide to smooth, realistic shadows in CSS - DEV Community
Powerful less mixins - Made Simple Media
What is wrong with my box-shadow SASS @Mixin? - Stack Overflow