In the reference list I find fifteen references to Kurt Jäger and one to Kurt Jaeger. I believe all the references should say “Kurt Jaeger”. And the reference codes shouldn't begin with Jäg.
The two Kurt Jaeger books I own (J and Jäg 6 FHI) use Jaeger and never Jäger on the cover and inside.
Looking at amazon.de there are scores of books by Kurt Jäger or Kurt Jaeger (multiple authors), but for the numismatic books it is Jaeger.
I found images of many of the Kurt Jaeger reference books and in each case the form listed is Jaeger, (The photos are of the cover, but when I've found books by an author named “Jäger” I see “Jäger” on the cover.)
Using a name form other than what is on the book makes the references harder to find. I searched for Jaeger at one point and only found one, when I knew there should be more.
(There is no other use of Jäger in the reference list other than for Kurt Jaeger.)
Edit: Fixed typo and added statement to change reference codes.
