https://researchbriefings.files.parliament.uk/documents/CBP-7212/CBP-7212.pdf
https://blogs.lse.ac.uk/brexit/2021/01/11/article-16-of-the-ireland-northern-ireland-protocol-offers-no-quick-fix/
https://www.gov.uk/guidance/status-of-eu-nationals-in-the-uk-what-you-need-to-know