PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Bölsche, Johanna Dating: 24.12.1904
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: de Gruyter, Walter Dating: 22.11.1904
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Friederici, Erna Dating: 23.12.1904