BRIEF OHNE UMSCHLAG Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 04.10.1867
BRIEF [O.A.] Focke, Gustav Waldemar Author: Focke, Gustav Waldemar Recipient: Haeckel, Ernst Dating: 29.10.1867
BRIEF OHNE UMSCHLAG Kottmeier, Johann Friedrich Author: Kottmeier, Johann Friedrich Recipient: Haeckel, Ernst Dating: 06.07.1867