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You could read through the relevant Wikipedia pages for an overview: https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...

Wikipedia is rarely a good introduction for laymen. It tends to be a great reference for people already in the field.

That's true in mathematics, but I find for any other subject it's a great reference for anyone intelligent enough to understand the subject.

(One might remark that I'm just not intelligent enough to understand advanced mathematics, and they might be right...)