https://blogs.lse.ac.uk/brexit/2019/08/12/boris-johnsons-real-agenda-the-singapore-scenario/
https://www.rand.org/pubs/research_reports/RR1786.html
http://www.resolutionfoundation.org/app/uploads/2017/10/Changing-Lanes-3.pdf
http://blogs.lse.ac.uk/brexit/2018/05/15/switzerland-wanted-more-immigration-controls-but-economic-self-interest-will-probably-prevail/