BRIEF [O.A.] Wölfling, Friedrich Author: Wölfling, Friedrich Recipient: Haeckel, Ernst Dating: 10.06.1912
BRIEF [O.A.] Wölfling, Friedrich Author: Wölfling, Friedrich Recipient: Haeckel, Ernst Dating: 16.06.1912
BRIEF [O.A.] Witte, Julius Author: Witte, Julius Recipient: Haeckel, Ernst Corporation: Redaktion des General-Anzeigers Badische Neueste Nachrichten Dating: 17.06.1912
BRIEF [O.A.] Haeckel, Siegfried Author: Haeckel, Siegfried Recipient: Haeckel, Ernst Dating: 15.02.1912