http://bruegel.org/2015/05/corruptionomics-in-italy/
https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820%2930468-2
https://www.politico.eu/article/germany-9-euro-ticket-train-public-transport/?utm_source=POLITICO.EU&utm_campaign=41557aa1fc-EMAIL_CAMPAIGN_2022_10_14_11_29&utm_medium=email&utm_term=0_10959edeb5-41557aa1fc-190380769
https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef19045en.pdf