http://blogs.lse.ac.uk/brexit/2018/05/15/switzerland-wanted-more-immigration-controls-but-economic-self-interest-will-probably-prevail/
https://www.socialeurope.eu/wp-content/uploads/2018/05/BP1-Devolution.pdf
https://publications.parliament.uk/pa/ld201719/ldselect/ldconst/69/69.pdf