Siman, M. (2026) “Equality Through Differentiation: Opt-Outs and Enhanced Cooperation as Expressions of Sovereignty”, in Author, T. and Author, T. (eds.) Unequal Equals? The Status of Member States in an Integrating European Union. Miskolc–Budapest: Studies of the Central European Professors’ Network, pp. 235–277. doi:10.54237/profnet.2026.dsuesmsieu_7.