No single resource covers everything perfectly.

Many students find it helpful to watch a video first to get an initial sense of a topic, then do some reading for depth, then return to the video after the reading has provided more context.

The resources listed here are all free and widely used. They are not the only good options — individual instructors, university libraries, and course materials may provide equally useful alternatives.

The goal is not to use all of these resources.

The goal is to find the combination that helps ideas become clear.