https://www.publications.parliament.uk/pa/ld201617/ldselect/ldeucom/169/169.pdf
https://ukandeu.ac.uk/why-david-cameron-called-the-2016-referendum/?mc_cid=dcb6ed542c&mc_eid=815b1928ec
https://uk.reuters.com/article/uk-britain-eu-options/stairway-to-brexit-barnier-maps-out-uks-canadian-path-idUKKBN1ED23R