BRIEF [O.A.] Arbesser, Cäsar v. Author: Arbesser, Cäsar v. Recipient: Haeckel, Ernst Dating: 08.04.1911
BRIEF [O.A.] Arbesser, Cäsar v. Author: Arbesser, Cäsar v. Recipient: Haeckel, Ernst Dating: 16.04.1911
BRIEF [O.A.] Faber, George Louis Author: Faber, George Louis Recipient: Haeckel, Ernst Corporation: British Consulate Dating: 28.12.1889
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Familie Haeckel in Potsdam Dating: 21.04.1878
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Familie Haeckel in Potsdam Dating: 26.04.1878
BRIEF [O.A.] Eurinac, Adolf E... Author: Eurinac, Adolf E... Recipient: Haeckel, Ernst Dating: 18.09.1887