https://blogs.lse.ac.uk/brexit/2019/04/15/brexit-lessons-from-the-silesian-backstop-of-1919-25/
http://www.cer.org.uk/sites/default/files/insight_JS_9.5.17.pdf
http://www.oliverwyman.com/content/dam/oliver-wyman/v2/publications/2018/march/Oliver-Wyman_Clifford-Chance-The-Red-Tape-Cost-of-Brexit.pdf
http://voxeu.org/system/files/epublication/Brexit_Beckons_VoxEU.pdf