ANSICHTSKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Focke, Wilhelm Olbers Dating: 22.02.1916
ANSICHTSKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Nebuschka, Marie Luise Dating: 14.07.1916
ANSICHTSKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Focke, Wilhelm Olbers Dating: 15.06.1916