
https://www.hks.harvard.edu/sites/default/files/centers/mrcbg/programs/senior.fellows/Brexit%20Paper%20IV%20-%20Final%20Paper.pdf

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/637748/Future_customs_arrangements_-_a_future_partnership_paper.pdf

https://www.parliament.uk/documents/lords-committees/eu-select/Third-Interparliamentary-Forum-on-Brexit-statement.pdf