https://publications.parliament.uk/pa/cm201719/cmselect/cmhaff/421/421.pdf
https://ec.europa.eu/commission/sites/beta-political/files/position-paper-public-procurement_en.pdf
https://docs.iza.org/dp16728.pdf
https://www.bloomberg.com/news/articles/2019-09-11/world-s-oldest-customs-union-and-u-k-reach-a-post-brexit-deal