https://www.gov.uk/government/news/david-davis-speech-to-the-suddeutsche-zeitung-economic-summit
http://reutersinstitute.politics.ox.ac.uk/risj-review/sympathetic-unconcerned-how-europes-media-cover-brexit
http://cer.eu/in-the-press/speech-michel-barnier-future-eu-conference
https://www.instituteforgovernment.org.uk/sites/default/files/publications/IfG_Brexit_customs_WEB.pdf