https://ukandeu.ac.uk/wp-content/uploads/2023/05/Divergence-Tracker-7-FINAL.pdf
https://www.congress.gov/117/bills/s3572/BILLS-117s3572is.xml
https://ukandeu.ac.uk/why-david-cameron-called-the-2016-referendum/?mc_cid=dcb6ed542c&mc_eid=815b1928ec
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/899991/200713_BPDG_-_Border_Operating_Model_FINAL_1320_edit.pdf