Nozick, Robert (1974). Anarchy, State, and Utopia. Basic Books. hlm. 34. In this subsection, Nozick makes a case for forceful self-defence, which he explicitly states being compatible with non-aggression principle.
Mack, Eric (30 May 2019). Zalta, Edward N., ed. The Stanford Encyclopedia of Philosophy. Metaphysics Research Lab, Stanford University – via Stanford Encyclopedia of Philosophy.