https://bdi.eu/media/pressecenter/#/artikel/news/brexit-wirft-seine-schatten-voraus/
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/637748/Future_customs_arrangements_-_a_future_partnership_paper.pdf
http://ukandeu.ac.uk/wp-content/uploads/2017/06/One-year-on.pdf
http://www.europarl.europa.eu/RegData/etudes/IDAN/2017/599352/EPRS_IDA%282017%29599352_EN.pdf