https://blogs.lse.ac.uk/brexit/2019/04/15/brexit-lessons-from-the-silesian-backstop-of-1919-25/
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/710147/DATA_-_FINAL.pdf
http://2ihmoy1d3v7630ar9h2rsglp-wpengine.netdna-ssl.com/wp-content/uploads/2019/09/190926-Brexit-and-the-Belfast-Good-Friday-Agreement-Final-report.pdf
http://www.cesifo-group.de/portal/page/portal/DocBase_Service/studien/Studie-2017-Felbermayr-etal-Brexit-79843.pdf