https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf
http://www.acea.be/uploads/publications/ACEA_position_paper-Brexit.pdf
http://foodresearch.org.uk/wp-content/uploads/2016/03/Food-and-Brexit-briefing-paper-2.pdf
http://www.lawsociety.org.uk/news/stories/leaving-in-an-orderly-fashion-our-approach-to-brexit/