Siman, Michael. “Equality Through Differentiation: Opt-Outs and Enhanced Cooperation As Expressions of Sovereignty”. In Unequal Equals? The Status of Member States in an Integrating European Union, edited by David Sehnálek, 235–277. Miskolc–Budapest: Studies of the Central European Professors’ Network, 2026. Accessed September 8, 2026. https://cea.omp.testing.qulto.eu:443/index.php/ceaprofnet/catalog/book/65/chapter/702.