https://www.rand.org/pubs/research_reports/RR2200.html
http://fedtrust.co.uk/the-2017-general-election-a-mandate-for-brexit/
http://www.rug.nl/research/portal/files/41711829/cesifo1_wp6448.pdf
https://ec.europa.eu/commission/sites/beta-political/files/customs_controls_0.pdf