https://www.gov.uk/government/news/programme-for-fourth-round-of-uk-eu-article-50-negotiations
https://www.instituteforgovernment.org.uk/sites/default/files/publications/negotiating-brexit-preparing-talks-uk-future-relationship-eu-FINAL_1.pdf
http://www.britishchambers.org.uk/press-office/press-releases/bcc-open-letter-to-pm-businesses-need-clarity-on-brexit.html
http://www.voxeurop.eu/en/2017/eu-uk-relations-5120821