https://www.nao.org.uk/wp-content/uploads/2018/10/The-UK-border-preparedness-for-EU-exit.pdf
https://www.opendemocracy.net/uk/peter-geoghegan/growing-up-on-border-on-brexit-s-irish-problem?utm_source=Daily+Newsletter&utm_campaign=b906170335-DAILY_NEWSLETTER_MAILCHIMP&utm_medium=email&utm_term=0_717bc5d86d-b906170335-407405485
http://www.fdf.org.uk/news.aspx?article=7834
https://ec.europa.eu/commission/sites/beta-political/files/citizens-rights-essential-principles-draft-position-paper_en.pdf