https://publications.parliament.uk/pa/cm201719/cmselect/cmexeu/1778/1778.pdf
https://www.socialeurope.eu/2017/07/brexit-to-nowhere/
https://www.gov.uk/government/speeches/eu-speech-at-bloomberg
http://www.guengl.eu/uploads/news-documents/Working_paper_Border_controls_on_cross_border_trade_in_goods.pdf