Phelan, William (2012). "What Is Sui Generis About the European Union? Costly International Cooperation in a Self-Contained Regime". International Studies Review. 14 (3): 367–385. doi:10.1111/j.1468-2486.2012.01136.x.
Zalta, Edward N., ed. (26 April 2021). The Stanford Encyclopedia of Philosophy. Metaphysics Research Lab, Stanford University – via Stanford Encyclopedia of Philosophy.