https://socialeurope.eu/brexit-why-does-northern-ireland-matter-so-much
http://ukandeu.ac.uk/wp-content/uploads/2017/06/One-year-on.pdf
https://ec.europa.eu/commission/sites/beta-political/files/customs_controls_0.pdf
https://www.opendemocracy.net/anthony-barnett/why-brexit-won-t-work-eu-is-about-regulation-not-sovereignty?utm_source=Daily+Newsletter&utm_campaign=84fcef5dd0-DAILY_NEWSLETTER_MAILCHIMP&utm_medium=email&utm_term=0_717bc5d86d-84fcef5dd0-407405485