I navigated to the course site and turns out the professor directly links to pirated copies of comprehensive sources on libgen. Thought it was pretty funny that he doesn't care about copyright being a professor at a public university :-). The linked sites are down since the main site libgen.rs is down but if you know libgen you know how to get to other places.
Usually people don't explicitly post links to libgen in their public website, but the vast majority of mathematicians makes ample use of libgen and sci-hub without thinking twice
https://www.cip.ifi.lmu.de/~grinberg/t/22s/