https://www.theguardian.com/politics/2017/nov/10/brexit-date-is-not-irreversible-says-man-who-wrote-article-50-lord-kerr
http://www.voxeurop.eu/en/2017/eu-uk-relations-5120821
https://publications.parliament.uk/pa/cm201719/cmselect/cmfaff/780/780.pdf