Most of these images already are freely available on the Wikipedia commons, where they were shared with the intention of being freely used by other users. While the authors cite the illustrator, is she being compensated for her work? They're great illustrations -- you'll rarely find better. But I have penalize the company for selling what already is being given away for free.
Here's the wikipedia link: http://en.wikipedia.org/wiki/Category:Approved_din-
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