https://www.socialeurope.eu/wp-content/uploads/2018/05/BP1-Devolution.pdf
https://docs.iza.org/dp16728.pdf
http://www.europarl.europa.eu/RegData/etudes/STUD/2017/602028/IPOL_STU(2017)602028_EN.pdf
https://www.gov.uk/government/news/david-davis-opening-remarks-at-the-start-of-the-fourth-round-of-eu-exit-negotiations