https://thecritic.co.uk/take-trade-experts-and-their-models-with-a-bucket-of-salt/
https://institute.global/news/customs-and-exiting-european-union
http://www.parliament.uk/documents/commons-committees/Exiting-the-European-Union/17-19/Cross-Whitehall-briefing/EU-Exit-Analysis-Cross-Whitehall-Briefing.pdf
http://www.europarl.europa.eu/cmsdata/115748/IPOL_IDA(2017)583130_EN.pdf