http://www.voxeurop.eu/en/2017/eu-uk-relations-5120821
https://www.instituteforgovernment.org.uk/sites/default/files/publications/IfG_Brexit_customs_WEB.pdf
http://blogs.lse.ac.uk/brexit/2017/07/05/bloody-difficult-britain-has-already-blown-its-chances-of-a-good-deal-from-the-eu27/
https://bdi.eu/media/user_upload/20171005_Pressemitteilung_Brexit.pdf