http://docs.dpaq.de/10395-0216-euco-conclusions.pdf
https://www.socialeurope.eu/sweden-achievements-uncertainty
https://dbei.gov.ie/en/Publications/Publication-files/Ireland-and-the-Impacts-of-Brexit.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/