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

https://www.open-britain.co.uk/new_research_trade_deals_with_five_key_countries_could_take_26_years_to_negotiate

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/650455/customs_bill_white_paper_print.pdf