BRIEF [O.A.] ...lemann, Theodor Author: ...lemann, Theodor Recipient: Haeckel, Ernst Dating: 10.04.1905
BRIEF [O.A.] Ziegler, Heinrich Ernst Author: Ziegler, Heinrich Ernst Recipient: Haeckel, Ernst Dating: 24.11.1900
BRIEF [O.A.] Sloman, Robert Miles jr. Author: Sloman, Robert Miles jr. Recipient: Haeckel, Ernst Dating: 27.02.1902
