https://ec.europa.eu/commission/publications/position-paper-essential-principles-citizens-rights_en
http://fedtrust.co.uk/the-2017-general-election-a-mandate-for-brexit/
http://www.fdf.org.uk/news.aspx?article=7834
https://ukandeu.ac.uk/wp-content/uploads/2021/11/Brexit-and-Services-Trade-Working-Paper.pdf