What are the different forms of access that have been provided to the basic level of knowledge? One could cite libraries, classrooms, laboratories, professors as sources of knowledge at a university, and studying at a university affords access to all of them. What is “single source access”?

I don’t think there’s a hard rule mitigating for or against “by,” I would tend to lean in favor of it, however. “Studying in the university” casts, to me, the notion of a specific time or moment of study, whereas “By studying…” conveys the general idea of study that, in turn, provided access to the desired knowledge.