https://www.gov.uk/government/publications/information-about-the-withdrawal-bill
https://ec.europa.eu/commission/sites/beta-political/files/outline_of_the_political_declaration.pdf
https://www.thetimes.co.uk/edition/news/irish-want-sea-border-with-uk-after-brexit-lvb6n35fq
http://www.europarl.europa.eu/cmsdata/115748/IPOL_IDA(2017)583130_EN.pdf