BRIEF [O.A.] Haeckel, Siegfried Author: Haeckel, Siegfried Recipient: Haeckel, Ernst Dating: 15.02.1906
BRIEF [O.A.] Straede, Lotte (geb. Hahn) Author: Straede, Lotte (geb. Hahn) Recipient: Haeckel, Ernst Dating: 06.01.1906