
https://publications.parliament.uk/pa/ld201719/ldselect/ldconst/69/69.pdf

http://www.reuters.com/article/us-britain-eu-verhofstadt-idUSKBN19V0WP

https://www.iwh-halle.de/fileadmin/user_upload/publications/iwh_discussion_papers/iwh-discussion-paper_2019-04_Brautzsch_Holtemoeller.pdf