
https://blogs.lse.ac.uk/brexit/2019/12/03/a-missed-opportunity-revisiting-the-euro-referendum-that-never-was-from-a-historical-perspective/

http://blogs.sussex.ac.uk/uktpo/files/2017/11/Briefing-Paper-11.pdf

https://ec.europa.eu/commission/publications/position-paper-essential-principles-citizens-rights_en