https://www.gov.uk/guidance/status-of-eu-nationals-in-the-uk-what-you-need-to-know
http://oegfe.at/wordpress/2017/05/the-free-movement-of-workers-within-the-eu-and-the-case-of-austria-balancing-distortions-and-adding-value-op-ed-paul-schmidt-the-european-financial-review/
https://www.llri.lt/wp-content/uploads/2018/06/Labour-Migration_3.pdf