https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef1714en.pdf
https://www.ccomptes.fr/system/files/2019-07/20190716-rapport-regimes-speciaux-retraite.pdf
https://www.gisreportsonline.com/r/sweden-immigrants-crisis/
http://www.ilo.org/wcmsp5/groups/public/—dgreports/—dcomm/—publ/documents/publication/wcms_548950.pdf