BRIEF OHNE UMSCHLAG Ammann, Wilhelm Author: Ammann, Wilhelm Recipient: Haeckel, Ernst Dating: 30.12.1878
BRIEF OHNE UMSCHLAG Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 15.04.1878
BRIEF OHNE UMSCHLAG Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 20.07.1878