
https://www.nao.org.uk/wp-content/uploads/2016/02/Managing-the-supply-of-NHS-clinical-staff-in-England.pdf

http://blogs.lse.ac.uk/brexit/2018/05/15/switzerland-wanted-more-immigration-controls-but-economic-self-interest-will-probably-prevail/

http://researchbriefings.files.parliament.uk/documents/CBP-7840/CBP-7840.pdf