Oberstleutnant Udet
<bdi><a href="https://en.wikipedia.org/wiki/en:Nicola_Perscheid" class="extiw" title="w:en:Nicola Perscheid"><span title="German photographer (1864-1930)">Nicola Perscheid</span></a>
</bdi>
Amtliche Kriegs-Depeschen. 8. Band. Nationaler Verlag, Berlin, o.A. <a rel="nofollow" class="external autonumber" href="https://archive.org/details/amtlichekriegsde08contuoft">[1]</a>