http://www.consilium.europa.eu//media/32504/xt21004-ad01re02en18.pdf
https://institute.global/news/customs-and-exiting-european-union
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/642542/Science_and_innovation_paper.pdf
https://publications.parliament.uk/pa/ld5801/ldselect/ldeucom/248/248.pdf