http://www.conservativehome.com/parliament/2016/04/theresa-mays-speech-on-brexit-full-text.html
https://ec.europa.eu/commission/publications/terms-reference-article-50-treaty-european-union-negotiations_en
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/640485/Technical_note_on_Functionality_and_Protocol_7.pdf
https://www.iod.com/Portals/0/PDFs/Campaigns%20and%20Reports/Europe%20and%20trade/IoD-Customising-Brexit.pdf?ver=2018-02-15-083137-800