https://www.sbs.strath.ac.uk/economics/fraser/20171129/GMB-Brexit-report.pdf
https://institute.global/news/customs-and-exiting-european-union
http://www.oecd.org/eco/outlook/economic-forecast-summary-united-kingdom-oecd-economic-outlook-june-2017.pdf
http://blogs.lse.ac.uk/brexit/2018/09/25/brexit-has-become-unnegotiable-theresa-may-has-a-constitutional-duty-to-admit-that-truth/