No library in the world can have everything all at once, but we can borrow it from someone else!
It's called Interlibrary Loan, and it is your friend. Just make sure to do your research at least a week ahead of time—the last thing you want is to find the perfect book or article but not be able to use it because you have to get it through interlibrary loan and your paper is due tomorrow.
Not sure how to use ILL? Ask a librarian!