https://www.waz.de/politik/gabriel-brexit-vertrag-als-modell-fuer-eu-tuerkei-beziehung-id212938393.html
https://www.parliament.uk/documents/commons-committees/culture-media-and-sport/Background%20paper%20-%202016%20Referendum%20Expenses%20Opinion%20-%20Matrix%20Chambers.pdf
https://ec.europa.eu/commission/sites/beta-political/files/aviation.pdf