
https://blogs.lse.ac.uk/europpblog/2023/10/17/why-differentiation-is-now-at-the-heart-of-europes-political-system/

https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef1710en.pdf

https://theconversation.com/idea-of-eu-citizenship-still-intangible-for-most-europeans-230994