http://uk.reuters.com/article/uk-britain-eu-immigration-idUKKBN18L0XG
https://www.esri.ie/system/files/publications/JR2.pdf
https://www.cer.eu/sites/default/files/insight_JS_JP_17.1.23.pdf
https://www.socialeurope.eu/romania-and-bulgaria-stuck-in-eus-second-tier