https://www.nao.org.uk/wp-content/uploads/2018/10/The-UK-border-preparedness-for-EU-exit.pdf
https://ukandeu.ac.uk/trade-migration-and-brexit/
https://www.gov.uk/government/speeches/pm-commons-statement-on-eu-reform-and-referendum-22-february-2016
https://www.socialeurope.eu/2017/06/britains-deepening-confusion/