Find lots of info at the Gates of Vienna here (which was the inspiration for the first design I made of “Widerstand” plus the German-Resistance flag motif, back in October 2015). I like this second one even more.
Here’s some background from Wikipedia on those 1940’s anti-NAZI flags which forms the center of this design.
Couldn’t find my old paperback to photograph and couldn’t spare the time to search for it. (It’s a terrific book, BTW.)