https://www.nao.org.uk/wp-content/uploads/2018/10/The-UK-border-preparedness-for-EU-exit.pdf
https://blogs.lse.ac.uk/brexit/2018/10/30/after-brexit-the-uk-should-be-able-to-re-enter-the-eu-if-it-wishes-to-do-so/
https://www.bloomberg.com/news/articles/2017-06-01/soros-says-brexit-may-last-5-years-and-cause-immense-damage?cmpid=BBBXT060217_BIZ&utm_medium=email&utm_source=newsletter&utm_term=170602&utm_campaign=brexit
http://www.consilium.europa.eu//media/32504/xt21004-ad01re02en18.pdf