https://www.euronews.com/2018/09/25/why-is-the-irish-border-issue-so-complex-euronews-answers
http://www.cbi.org.uk/index.cfm/_api/render/file/?method=inline&fileID=7C026F7C-746E-4795-90EFCC69B2FB6756
https://www.wto.org/english/res_e/booksp_e/wtr23_e/wtr23_e.pdf