
https://static1.squarespace.com/static/5afc0bbbf79392ced8b73dbf/t/5b07d7ce1ae6cf2a4178f587/1527240672975/SGC_Full_Report.pdf

https://www.nber.org/system/files/working_papers/w27488/w27488.pdf

https://www.consilium.europa.eu/media/54923/peg-letter-to-pec-march2022-signed.pdf