https://www.linkiesta.it/2020/05/cosa-ha-davvero-deciso-la-corte-tedesca-bce-quantitative-easing/
https://www.ifs.org.uk/publications/14778
https://taxfoundation.org/flat-tax-state-income-tax-reform/
https://www.ecb.europa.eu/home/search/review/pdf/ecb.strategyreview_monpol_strategy_statement.en.pdf