https://ecipe.org/blog/the-letta-report-the-good-and-the-bad/
https://blogs.lse.ac.uk/europpblog/2022/10/06/the-european-political-community-a-step-toward-differentiated-integration-in-europe/
https://www.opendemocracy.net/can-europe-make-it/kieran-oberman/does-catalonia-have-right-to-secede?utm_source=Daily+Newsletter&utm_campaign=9960ef2d4f-DAILY_NEWSLETTER_MAILCHIMP&utm_medium=email&utm_term=0_717bc5d86d-9960ef2d4f-407405485
https://www.diw.de/documents/publikationen/73/diw_01.c.578096.de/18-7-3.pdf