https://www.rand.org/pubs/research_reports/RR2200.html
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/648148/September_-_Joint_technical_note_on_the_comparison_of_EU-UK_positions_on_citizens__rights.pdf
https://www.nao.org.uk/wp-content/uploads/2022/05/Regulating-after-EU-Exit.pdf
http://fedtrust.co.uk/views-from-the-federal-trust/free-movement-and-migration/