https://www.consilium.europa.eu/media/54923/peg-letter-to-pec-march2022-signed.pdf
https://www.tandfonline.com/doi/full/10.1080/09692290.2022.2107043
https://cepr.org/sites/default/files/policy_insights/PolicyInsight92.pdf
https://www.hesa.ac.uk/data-and-analysis/publications/finances-2015-16/introduction