https://www.gov.uk/government/news/programme-for-fourth-round-of-uk-eu-article-50-negotiations
https://ec.europa.eu/commission/commissioners/2014-2019/andriukaitis/blog/likening-eu-ussr-not-unreasonable_en
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/665871/December_-_Joint_technical_note_on_the_comparison_of_EU-UK_positions_on_citizens__rights.pdf
https://publications.parliament.uk/pa/ld5801/ldselect/ldeucom/4/4.pdf