https://www.rand.org/pubs/research_reports/RR2200.html
https://researchbriefings.files.parliament.uk/documents/CBP-7212/CBP-7212.pdf
https://www.instituteforgovernment.org.uk/sites/default/files/publications/negotiating-brexit-preparing-talks-uk-future-relationship-eu-FINAL_1.pdf
https://ec.europa.eu/commission/sites/beta-political/files/financial-settlement-essential-principles-draft-position-paper_en.pdf