BRIEF [O.A.] Friedenthal, Albert Author: Friedenthal, Albert Recipient: Haeckel, Ernst Dating: 18.07.1909
BRIEF OHNE UMSCHLAG Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 07.02.1909
BRIEF OHNE UMSCHLAG Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 18.06.1909
BRIEF OHNE UMSCHLAG Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 21.06.1909
BRIEF OHNE UMSCHLAG Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 08.09.1909
BRIEF OHNE UMSCHLAG Geheeb, Adalbert Author: Geheeb, Adalbert Recipient: Haeckel, Ernst Dating: 11.03.1909