BRIEF [O.A.] Hertwig, Richard Author: Hertwig, Richard Recipient: Breitenbach, Wilhelm Dating: 10.07.1909
BRIEF [O.A.] Straede, Lotte (geb. Hahn) Author: Straede, Lotte (geb. Hahn) Recipient: Haeckel, Ernst Dating: 15.02.1909
BRIEF [O.A.] Haeckel, Siegfried Author: Haeckel, Siegfried Recipient: Haeckel, Ernst Dating: 23.12.1909