https://policyexchange.org.uk/wp-content/uploads/2017/07/After-Brexit-will-Ireland-be-next-to-exit-1.pdf
https://researchbriefings.files.parliament.uk/documents/CBP-7212/CBP-7212.pdf
https://blogs.lse.ac.uk/brexit/2019/10/09/northern-ireland-depends-on-the-eus-fluid-borders-for-survival/