explored 
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If you know any good books about the #Ruhrgebiet, please leave comment below 
@pixeltracker
I can recommend: Kataoka, A., Mathias, R., Meid, P.T., Pascha, W., Shimada, S.: "Japanische Bergleute im Ruhrgebiet", Klartext 2012
It nicely describes a less well know aspect of industrial culture.
@Frank Thank you very much! I was not aware about the fact that "… over 400 Japanese miners worked in the Ruhr area between 1957 and 1965". Thanks for this book 
@Frank @pixeltracker Wow, TIL. Thanks!