https://www.w3schools.com/sass/default.php
https://medium.com/@kish.siva/how-to-start-using-sass-in-visual-studio-code-5469787f18bf
https://tutorialzine.com/2016/01/learn-sass-in-15-minutes
https://www.tutorialspoint.com/sass/index.htm
https://css-tricks.com/the-sass-ampersand/
Tutorial muy bueno con ejemplos