https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef20023en.pdf
http://library.fes.de/pdf-files/iez/13375.pdf
https://cps.org.uk/wp-content/uploads/2021/09/210918224828-CPSWELFAREPAPER1.pdf
https://www.ccomptes.fr/system/files/2019-07/20190716-rapport-regimes-speciaux-retraite.pdf