http://fedtrust.co.uk/views-from-the-federal-trust/free-movement-and-migration/
http://www.cer.eu/sites/default/files/bulletin_118_js-sl_article2.pdf
https://www.opendemocracy.net/en/opendemocracyuk/customs-union-leaves-everything-play-trade-justice/?utm_source=Daily+Newsletter&utm_campaign=f531c721c4-DAILY_NEWSLETTER_MAILCHIMP&utm_medium=email&utm_term=0_717bc5d86d-f531c721c4-407405485
http://ourglobalfuture.com/wp-content/uploads/2017/05/Global-Future-The_case_for_immigration.pdf