https://www.boeckler.de/pdf/v_2018_04_26_27_arg_co_determ.pdf
https://www.llri.lt/wp-content/uploads/2018/06/Labour-Migration_3.pdf
https://www.cer.eu/sites/default/files/insight_JS_JP_17.1.23.pdf
https://www.publications.parliament.uk/pa/ld201314/ldselect/ldeucom/164/164.pdf