BILDPOSTKARTE Aigner, Eduard Author: Aigner, Eduard Recipient: Haeckel, Ernst Corporation: Deutscher Monistenbund Dating: 09.09.1913
BILDPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Verworn, Max; Verworn, Josephine Dating: 29.12.1903
BILDPOSTKARTE Grimsehl, Carl; Grimsehl, M. Author: Grimsehl, Carl; Grimsehl, M. Recipient: Haeckel, Ernst Dating: 22.09.1917