https://ec.europa.eu/commission/sites/beta-political/files/position-paper-public-procurement_en.pdf
https://www.regjeringen.no/globalassets/upload/kilde/fkd/red/2004/0009/ddd/pdfv/228920-nilf_rapport_2004_9_s.pdf
https://www.cesifo-group.de/DocDL/ifoDD_18-01_03-09_Ochsner.pdf