BRIEF [O.A.] Fuchsel, A... Author: Fuchsel, A... Recipient: Haeckel, Ernst Corporation: Deutscher Monistenbund, Ortsgruppe Weimar Dating: 12.08.1919
BRIEF [O.A.] Bojanowski, Paul von Author: Bojanowski, Paul von Recipient: Haeckel, Ernst Corporation: Grossherzogliche Bibliothek Dating: 13.05.1903
BRIEF [O.A.] Bojanowski, Paul von Author: Bojanowski, Paul von Recipient: Haeckel, Ernst Dating: 25.05.1903
BRIEF [O.A.] Kellermann, Hermann Author: Kellermann, Hermann Recipient: Haeckel, Ernst Corporation: Alexander Duncker Verlag Dating: 01.01.1914
BRIEF [O.A.] Kellermann, Hermann Author: Kellermann, Hermann Recipient: Haeckel, Ernst Dating: 31.12.1905
BRIEF [O.A.] Kiepenheuer, Gustav Author: Kiepenheuer, Gustav Recipient: Haeckel, Ernst Corporation: Gustav Kiepenheuer Verlag in Weimar Dating: 14.09.1914
BRIEF [O.A.] Knobloch, Henriette von Author: Knobloch, Henriette von Recipient: Haeckel, Ernst Dating: 08.10.1913
BRIEF [O.A.] Bojanowski, Paul von Author: Bojanowski, Paul von Recipient: Haeckel, Ernst Dating: 11.12.1914