https://www.destatis.de/Europa/EN/Topic/Economy-Finance/Debt.html
https://www.imk-boeckler.de/download-proxy-for-faust/download-pdf?url=http%3A%2F%2F217.89.182.78%3A451%2Fabfrage_digi.fau%2Fp_imk_report_159e_2020.pdf%3Fprj%3Dhbs-abfrage%26ab_dm%3D1%26ab_zeig%3D8946%26ab_diginr%3D8482
https://www.strategie.gouv.fr/sites/strategie.gouv.fr/files/atoms/files/fs-2020-rapport-isf-octobre.pdf
https://www.foreignaffairs.com/united-states/2008-crisis-never-saw-coming