Steinkohleförderung in Preußen 1817-1870 (in 1000 t) (Zahlen nach sozialgeschichtliches Arbeitsbuch 1, S.63f.)
<a href="//commons.wikimedia.org/wiki/User:Machahn" title="User:Machahn">Machahn</a> 09:13, 14 October 2006 (UTC)
CC BY-SA 3.0
This  diagram was created with <a href="https://en.wikipedia.org/wiki/Microsoft_Excel" class="extiw" title="w:Microsoft Excel">Microsoft Excel</a>.