http://fedtrust.co.uk/after-the-election-comes-the-painful-brexit-reality/
https://publications.parliament.uk/pa/cm201719/cmselect/cmhaff/421/421.pdf
https://yougov.co.uk/news/2017/04/26/voting-intention-conservatives-45-labour-29-25-26-/
http://www.res.org.uk/view/art4Apr17Features.html