https://ukandeu.ac.uk/long-read/the-protocol-post-brexit-northern-ireland/?mc_cid=9de7c359e6&mc_eid=815b1928ec
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/725288/The_future_relationship_between_the_United_Kingdom_and_the_European_Union.pdf
https://publications.parliament.uk/pa/ld201719/ldselect/ldconst/69/69.pdf