https://publications.parliament.uk/pa/cm201719/cmselect/cmniaf/329/329.pdf
http://www.cesifo-group.de/portal/page/portal/DocBase_Service/studien/Studie-2017-Felbermayr-etal-Brexit-79843.pdf
https://www.euronews.com/2018/09/25/why-is-the-irish-border-issue-so-complex-euronews-answers
http://www.fdf.org.uk/news.aspx?article=8062