https://www.socialeurope.eu/2017/07/german-wages-need-rise/
https://theconversation.com/fact-check-does-immigration-have-an-impact-on-wages-or-employment-83666
https://www.esri.ie/system/files/publications/SUSTAT95_0.pdf
http://library.fes.de/pdf-files/iez/13375.pdf