https://publications.parliament.uk/pa/ld5801/ldselect/ldeucom/4/4.pdf
https://centreonconstitutionalchange.ac.uk/sites/default/files/2021-04/Union%20at%20the%20Crossroads.pdf
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/761852/05_December-_EU_Exit_Attorney_General_s_legal_advice_to_Cabinet_on_the_Withdrawal_Agreement_and_the_Protocol_on_Ireland-Northern_Ireland.pdf
https://publications.parliament.uk/pa/cm200203/cmhansrd/vo021126/debtext/21126-17.htm