https://www.gov.uk/government/news/pms-open-letter-to-eu-citizens-in-the-uk
http://www.parliament.uk/documents/commons-committees/Exiting-the-European-Union/17-19/Cross-Whitehall-briefing/EU-Exit-Analysis-Cross-Whitehall-Briefing.pdf
https://publications.parliament.uk/pa/ld5801/ldselect/ldeucom/248/248.pdf
https://www.cnas.org/publications/podcast/luke-coffey-on-brexit-and-the-future-of-the-special-relationship