
https://www.brookings.edu/wp-content/uploads/2018/03/fp_20180316_future_political_warfare.pdf

https://feps-europe.eu/wp-content/uploads/2024/07/PP25-WEB_PP.pdf

https://blogs.lse.ac.uk/europpblog/2021/10/22/de-facto-differentiation-in-action-why-poland-will-stay-in-the-eu-with-or-without-the-blessing-of-brussels/