PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Altmann-Bronn, Ida Dating: 26.02.1913
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Sprenger, Gustav; Sprenger, Therese Dating: 13.05.1915
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Sprenger, Therese; Sprenger, Gustav Dating: 22.07.1910
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Sprenger, Therese; Ernst Sprenger Dating: 23.03.1913
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Hauptmann, Gerhart Dating: 15.11.1912