https://www.spectator.co.uk/article/full-text-top-uk-brexit-negotiator-david-frost-on-his-plans-for-an-eu-trade-deal
https://www.gov.uk/guidance/status-of-eu-nationals-in-the-uk-what-you-need-to-know
https://www.socialeurope.eu/wp-content/uploads/2019/01/03_Brexit_Kroeger.pdf