https://bdi.eu/media/user_upload/20171005_Pressemitteilung_Brexit.pdf
http://www.cer.org.uk/sites/default/files/insight_js_st_9.6.17.pdf
http://www.oliverwyman.com/content/dam/oliver-wyman/v2/publications/2018/march/Oliver-Wyman_Clifford-Chance-The-Red-Tape-Cost-of-Brexit.pdf
http://www.guengl.eu/uploads/news-documents/Working_paper_Border_controls_on_cross_border_trade_in_goods.pdf