http://www.voxeurop.eu/en/2017/eu-uk-relations-5120821
http://ukandeu.ac.uk/an-utterly-pernicious-bill/
https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf
http://fedtrust.co.uk/our-work-on-europe/hard-brexit-international-trade-and-the-wto-scenario/