BRIEF [O.A.] Lehmann-Hohenberg, Johannes Author: Lehmann-Hohenberg, Johannes Recipient: Haeckel, Ernst Dating: 13.04.1914
BRIEF [O.A.] Kellermann, Hermann Author: Kellermann, Hermann Recipient: Haeckel, Ernst Corporation: Alexander Duncker Verlag Dating: 01.01.1914
BRIEF [O.A.] Kiepenheuer, Gustav Author: Kiepenheuer, Gustav Recipient: Haeckel, Ernst Corporation: Gustav Kiepenheuer Verlag in Weimar Dating: 14.09.1914
BRIEF [O.A.] Bojanowski, Paul von Author: Bojanowski, Paul von Recipient: Haeckel, Ernst Dating: 11.12.1914
BRIEF [O.A.] Thieme, Friedrich Author: Thieme, Friedrich Recipient: Haeckel, Ernst Dating: 08.01.1914