https://ec.europa.eu/commission/sites/beta-political/files/customs_controls_0.pdf
http://www.cesifo-group.de/portal/page/portal/DocBase_Service/studien/Studie-2017-Felbermayr-etal-Brexit-79843.pdf
http://www.bakermckenzie.com/-/media/files/insight/publications/brexit_tradeflows.pdf?la=en
https://www.iod.com/Portals/0/PDFs/Campaigns%20and%20Reports/Europe%20and%20trade/Business-of-Brexit.pdf?ver=2017-05-22-090428-150