BRIEF OHNE UMSCHLAG Bothe, Margarete Author: Bothe, Margarete Recipient: Haeckel, Ernst Dating: 01.12.1915
PORTRÄTPOSTKARTE Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 10.09.1907
BRIEF OHNE UMSCHLAG Altschul, Theodor Author: Altschul, Theodor Recipient: Haeckel, Ernst Dating: 28.05.1901