https://cer.org.uk/sites/default/files/bulletin_114_js_st_article1.pdf
https://hansard.parliament.uk/commons/2018-03-07/debates/65828E0C-3CC7-43AE-B5D2-B5F1B5D42A4C/EuropeanUnionCitizenship
https://www.sussex.ac.uk/webteam/gateway/file.php?name=briefing-paper-1.pdf&site=18
https://onlinelibrary.wiley.com/doi/epdf/10.1111/jcms.13386