BRIEF [O.A.] Falkenfeld, Falk Wolfgang Author: Falkenfeld, Falk Wolfgang Recipient: Haeckel, Ernst Dating: 15.02.1914
BRIEF [O.A.] Fischer, Jean Author: Fischer, Jean Recipient: Haeckel, Ernst Corporation: G. Reibold Nachf. Dating: 19.11.1901
POSTKARTE Fischer, Jean Author: Fischer, Jean Recipient: Haeckel, Ernst Corporation: G. Reibold Nachf. Dating: 25.02.1902