Possibly a very amateur question, yet I think is the best to know the answer as simply and as soon as possible.
Let me use a (not yet IRL, but only hypothetical) example: I want to write either my thesis, possibly even my PhD in the field of video games: construction, psychological relations and so on. I know a man, who's actively working on a successful indie game, and was working on Bioshock games as well - he has a great book in the matter, that is not only easy to read but I found it insightful, too.
What determines, if I'm allowed to use it as a credible resource of game design?
In general, what a resource should qualify to not cause controversies using it in any kind of publication? Or, if the question is too broad, let's focus on a BSc thesis.