https://www.gov.uk/government/news/joint-article-a-deep-and-special-partnership
https://ec.europa.eu/commission/sites/beta-political/files/slides_on_uk_technical_note_on_temporary_customs_arrangements.pdf
https://www.bloomberg.com/news/articles/2019-09-11/world-s-oldest-customs-union-and-u-k-reach-a-post-brexit-deal
https://docs.iza.org/dp16728.pdf