BRIEF [O.A.] Eberle, Cyprian Author: Eberle, Cyprian Recipient: Haeckel, Ernst Corporation: Monistischer Lesekreis Ulm Dating: 10.11.1904
BRIEF OHNE UMSCHLAG Finsterbusch, Helene Author: Finsterbusch, Helene Recipient: Haeckel, Ernst Dating: 25.12.1904
POSTKARTE Finsterbusch, Ludwig Author: Finsterbusch, Ludwig Recipient: Haeckel, Ernst Dating: 30.12.1904
