https://publications.parliament.uk/pa/cm200203/cmhansrd/vo021126/debtext/21126-17.htm
https://ukandeu.ac.uk/the-windsor-framework-where-have-all-the-rebels-gone/
http://blogs.lse.ac.uk/brexit/2018/09/25/brexit-has-become-unnegotiable-theresa-may-has-a-constitutional-duty-to-admit-that-truth/
https://www.iod.com/Portals/0/PDFs/Campaigns%20and%20Reports/Europe%20and%20trade/Business-of-Brexit.pdf?ver=2017-05-22-090428-150