https://blogs.lse.ac.uk/brexit/2019/04/15/brexit-lessons-from-the-silesian-backstop-of-1919-25/
https://www.instituteforgovernment.org.uk/printpdf/10590
https://www.instituteforgovernment.org.uk/explainers/eu-withdrawal-bill-amendments-and-debates
https://www.vdma.org/v2viewer/-/v2article/render/21059151