https://wiiw.ac.at/alternatives-in-the-design-of-sovereign-green-bonds-dlp-6412.pdf
https://www.brookings.edu/blog/up-front/2017/08/03/the-hutchins-center-explains-the-debt-limit/?utm_campaign=Brookings%20Brief&utm_source=hs_email&utm_medium=email&utm_content=54989469
https://think.ing.com/articles/four-scenarios-for-eurozone-reform-at-this-weeks-eu-summit/
https://www.sachverstaendigenrat-wirtschaft.de/fileadmin/dateiablage/gutachten/jg201819/JG2018-19_gesamt.pdf