https://blogs.lse.ac.uk/europpblog/2023/10/17/why-differentiation-is-now-at-the-heart-of-europes-political-system/
UKIN-State-of-the-EU-Report-1.pdf (ukandeu.ac.uk)
https://www.politico.eu/wp-content/uploads/2021/11/15/2021.11.15-Letter-to-EC-on-quality-of-replies-to-parliamentary-questions.pdf