https://www.socialeurope.eu/breaking-the-chains-subcontracting-in-the-eu
https://chemsec.org/app/uploads/2021/02/What-goes-around_210223.pdf
https://sipri.org/sites/default/files/2017-09/yb17-summary-eng.pdf
https://www.cps.org.uk/files/reports/original/201001000814-CPSUPWARDLYMOBILE2.pdf