https://www.raadvanstate.nl/publicaties/publicaties.html
file:///C:/Users/cooma_000/Downloads/EconPol_Policy_Report_02_2017_German_Account_Surplus.pdf
https://www.socialeurope.eu/2017/06/understanding-productivity-puzzle/
http://www.ecb.europa.eu/pub/pdf/other/ebart201703_01.en.pdf