Great introductory read - https://adamwathan.me/css-utility-classes-and-separation-of-concerns/
Tachyons case study - https://medium.com/hackernoon/full-re-write-with-tachyons-and-functional-css-a-case-study-part-1-635ccb5fb00b
Scalable CSS in Enterprise applications - https://mrmrs.cc/writing/scalable-css/