
https://www.europarl.europa.eu/doceo/document/B-9-2020-0098_EN.html?utm_source=POLITICO.EU&utm_campaign=3e49ba2509-EMAIL_CAMPAIGN_2020_02_13_05_53&utm_medium=email&utm_term=0_10959edeb5-3e49ba2509-190380769

https://www.regjeringen.no/globalassets/upload/kilde/fkd/red/2004/0009/ddd/pdfv/228920-nilf_rapport_2004_9_s.pdf

http://www.rug.nl/research/portal/files/41711829/cesifo1_wp6448.pdf