PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Heldburg, Helene von Dating: 30.05.1910
PORTRÄTPOSTKARTE Heldburg, Helene Freifrau von Author: Heldburg, Helene Freifrau von Recipient: Haeckel, Ernst Dating: 1907.??.?? [Sommer]
PORTRÄTPOSTKARTE Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 10.09.1905
PORTRÄTPOSTKARTE Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 24.12.1905
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Breitenbach, Wilhelm Dating: 01.10.1915
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: de Gruyter, Walter Dating: 22.11.1904