https://www.boeckler.de/pdf/p_wsi_report_52_2019.pdf
https://www.diw.de/documents/publikationen/73/diw_01.c.578096.de/18-7-3.pdf
https://www.bruegel.org/wp-content/uploads/2021/09/PC-2021-18-0909.pdf
http://www.economics-ejournal.org/economics/journalarticles/2017-10