Should I include self-studied courses/topics in undergraduate resume? I'm preparing my resume for internship application.

I have already included courses that I emphasized more on (reading extra advanced material outside of the course's material scope).

I read lots of books. Should I include topics that I self-studied to my resume as extracurricular knowledge?
I am sure that there is a very wide range of opinion/reaction to what some people call "self-study". For me (grad admissions in mathematics in the U.S.), evidence of interest in reading things beyond what coursework demands is an extremely positive and unusual indicator. That is, so far as people seem to let on, no one reads any math book that's not a textbook for a course they've registered for, does not read ahead, and so on. I don't understand it, although I've seen it for decades.

Yes, it is not as easy to "document" reading things as it is to document "grades in courses"... but my own opinion is that even excellent grades in courses form only a limited positive, since it refers to compliance, obedience, etc., even if at a challending level/rate/whatever.

That is, for me, mathematics is not merely a school subject, nor merely a thing that one might get research funding for... :)