https://policyscotland.gla.ac.uk/blog-sir-ivan-rogers-speech-text-in-full/
https://ukandeu.ac.uk/why-david-cameron-called-the-2016-referendum/?mc_cid=dcb6ed542c&mc_eid=815b1928ec
https://publications.parliament.uk/pa/cm201719/cmselect/cmcumeds/365/365.pdf