https://www.socialeurope.eu/how-to-treat-german-democracys-malaise
http://upceo.ceo.gencat.cat/wsceop/6508/Resumen%20en%20espa%C3%B1ol%20-874.pdf
http://www.diw.de/documents/publikationen/73/diw_01.c.562050.de/17-29.pdf
https://onlinelibrary.wiley.com/doi/10.1111/jcms.13415