
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

http://www.epc.eu/documents/uploads/pub_7576_northernirelandandbrexit.pdf

https://www.instituteforgovernment.org.uk/sites/default/files/publications/5704%20IFG%20-%20Frictionless%20Trade%20Web.pdf