BRIEF OHNE UMSCHLAG Pick, Klärchen Author: Pick, Klärchen Recipient: Haeckel, Ernst Dating: 07.03.1917
BRIEF [O.A.] Kerschner, Ludwig Author: Kerschner, Ludwig Recipient: Haeckel, Ernst Dating: 02.10.1901
BRIEF [O.A.] Mentz, Frida, geb. Kessel Author: Mentz, Frida, geb. Kessel Recipient: Haeckel, Ernst Dating: ??.02.1903
BRIEF [O.A.] Mentz, Frida, geb. Kessel Author: Mentz, Frida, geb. Kessel Recipient: Haeckel, Ernst Dating: ??.02.1903
BRIEF [O.A.] Neustadtel, Arthur Author: Neustadtel, Arthur Recipient: Haeckel, Ernst Dating: 04.07.1903
