BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 15.02.1899
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 15.02.1900
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 08.05.1900
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 01.11.1901
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 26.10.1903