https://www.brookings.edu/wp-content/uploads/2020/03/Del-Negro-et-al-Conference-Draft.pdf
http://www.russellgroup.ac.uk/media/5521/rg-international-students-june-2017.pdf
https://www.strategie.gouv.fr/sites/strategie.gouv.fr/files/atoms/files/coe-rapport-travail-non-declare-fevrier-2019.pdf
https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef1663en.pdf