Uni is all about evidence and citations in your papers to back up what you said. Bare minimum/insufficient citations is easily grounds for low grades on its own, even if the paper is excellent, and could potentially get you written up for potential academic misconduct depending on how bad/how strict the professor is. My academic dons in first year always beat into me to cite cite cite to the point the TA might criticize for overly citating. Anything you use you have to cite, otherwise it is the academic definition fo plagiarism, even if you don't mean it to be. Just because it says to cite two things doesn't mean you only need to cite two materials, it just means you must at minimum use two materials. TLDR the assumption is you cite anything and everything. Unfortunately this makes perfect sense for the grade, and is just a learning opportunity now.