https://euagenda.eu/upload/publications/untitled-124549-ea.pdf
https://www.cdu.de/artikel/europa-richtig-machen-getting-europe-right
https://www.foreignaffairs.com/europe/promise-and-peril-eu-expansion
https://ec.europa.eu/commission/publications/terms-reference-article-50-treaty-european-union-negotiations_en