How can i get resources to study CSS SASS and LESS?

Answer 1

CSS:

https://www.w3schools.com/css/
https://developer.mozilla.org/en-US/docs/Web/CSS
https://www.w3.org/Style/CSS/read.en.html

SASS (& SCSS)

https://sass-lang.com/

LESS

http://lesscss.org/

A mix of all:

https://css-tricks.com/

Some are appropriate for beginners, some are very technical and truly for intensive "study".

I hope this helps!

Answer 2

The internet itself is a great resource. Some libraries may carry some books regarding these languages. Colleges/Universities are also bound to be carrying several textbooks on these languages, especially during the first few weeks of a semester.