Does "In Anlehnung an" refer to XY et al.'s "Abbildungen"?
Who provided/created the illustrations for this paper? Somebody else than XY et al.? Were they in the style of/oriented towards other/similar illustrations by XY et al.?
Here are two references. 1) in Anlehnung an = orientiert an (= oriented/in the style of/loosely based on):
http://de.thefreedictionary.com/in Anlehnung anBut how are the paper's illustrations oriented towards XY et al.'s illustrations? Are they exact copies or do they look somewhat/very similar??
2) = sinngemäß/vgl. = c.f. -
http://de.wikipedia.org/wiki/Vgl. (search for "in Anlehnung an, sinngemäß/vgl.") -
but that could refer to a text rather than illustrations or, if it's indeed illustrations by XY et al., it would make the illustrations in your paper examples rather than "real" originals. They would be XY et al.'s creations (or at least theirs would be templates)?
I doubt the illustrations were created in the style of/based on XY et al.'s illustrations, but you've got the context.