http://www.cer.eu/sites/default/files/bulletin_118_js-sl_article2.pdf
http://www.rug.nl/research/portal/files/41711829/cesifo1_wp6448.pdf
https://publications.parliament.uk/pa/ld201719/ldselect/ldconst/69/69.pdf
https://institute.global/news/customs-and-exiting-european-union