There might be more than one word you could use; the first one that came to my mind was references. See Collins, Definition #7:
reference (n.) a source of information or facts
The word is also used as a modifier, as in reference books. There is also the term reference library, which is where a library shelves books that can't be checked out.
The word has a lot of meanings, so it's not a special-purpose word that specifically and exclusively means "textbooks, tutorials, educational and encyclopedia articles that one can read while studying a particular subject." However, if you were to write a paper, and you wanted to list all the sources you used to acquire information, you could do so under the heading REFERENCES.
Edit: As FumbleFingers mentioned in his comment, there is also the term literature. I've seen that when it refers to published works about a particular topic. As one helpful website says:
The first part of any scientific thesis, dissertation, or journal article is a literature review. Yes, I know it’s usually called the introduction. But that’s all the introduction really is – a review of everything anyone has ever written relevant to your topic, as well as a short statement as to what your aims are.