https://publications.parliament.uk/pa/ld201719/ldselect/ldconst/69/69.pdf
http://www.iata.org/whatwedo/Documents/economics/impact_of_brexit.pdf
https://www.gov.uk/guidance/status-of-eu-nationals-in-the-uk-what-you-need-to-know
http://www.ecfr.eu/page/-/Keeping_Europe_Safe_After_Brexit2.pdf