http://fedtrust.co.uk/the-2017-general-election-a-mandate-for-brexit/
https://publications.parliament.uk/pa/bills/cbill/58-03/0204/220204.pdf
https://www.gov.uk/government/news/david-davis-opening-remarks-at-the-start-of-the-third-round-of-eu-exit-negotiations
https://www.bloomberg.com/politics/articles/2017-04-26/brexit-risks-opening-pandora-s-box-of-trade-disputes-for-britain?cmpid=BBBXT042617_BIZ&utm_medium=email&utm_source=newsletter&utm_term=170426&utm_campaign=brexit