There's not much new to philosophy in some thousands of years, but comtemporary academic norms are that you credit your direct inspiration whenever possible, especially for a work meant to qualify you as well read and as a trustworthy peer.

If anything from 1926 onwards is fair game, then tons of work in the foundations of mathematics. And if you're willing to be slightly more more generous with your time-frame: Russel's paradox.

Philosophical Investigations (Wittgenstein), A Theory of Justice (Rawls), and The Structure of Scientific Revolutions (Kuhn) have all been pretty influential.