http://cep.lse.ac.uk/pubs/download/brexit11.pdf
https://ec.europa.eu/commission/sites/beta-political/files/joint_report.pdf
https://www.nber.org/system/files/working_papers/w28598/w28598.pdf
https://ec.europa.eu/commission/sites/beta-political/files/position-paper-public-procurement_en.pdf