http://www.icaew.com/-/media/corporate/files/technical/economy/brexit/eu-exit-charge.ashx
http://www.consilium.europa.eu//media/32504/xt21004-ad01re02en18.pdf
https://rusi.org/sites/default/files/briefingpaper-france-uk-2017.pdf
https://www.instituteforgovernment.org.uk/sites/default/files/publications/IfG_views-eu-27-v5_WEB.pdf