POSTKARTE Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 22.12.1910
POSTKARTE Mentz, Frida, geb. Kessel Author: Mentz, Frida, geb. Kessel Recipient: Haeckel, Emma Dating: 14.08.1910
POSTKARTE N.N. Author: N.N. Recipient: Haeckel, Ernst Corporation: Neuer Frankfurter Verlag G.m.b.H. Dating: 24.11.1910