
https://theconversation.com/why-the-eus-singapore-ruling-does-not-lead-to-a-smoother-brexit-road-for-britain-78116

http://www.guengl.eu/uploads/publications-documents/NSkoutarisGUENGLReportC_%28002%29.pdf

https://publications.parliament.uk/pa/ld201719/ldselect/ldeucom/15/15.pdf