https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/682894/Draft_Text_for_Discussion_-_Implementation_Period__1_.pdf
http://blogs.lse.ac.uk/brexit/2017/12/05/a-high-risk-game-of-chicken-is-being-played-over-the-irish-border/
https://www.bertelsmann-stiftung.de/de/themen/aktuelle-meldungen/2019/maerz/brexit-kostet-deutschland-bis-zu-zehn-milliarden-euro-jaehrlich/