BRIEF [O.A.] Baffi, Freia Gisela Author: Baffi, Freia Gisela Recipient: Haeckel, Ernst Dating: 16.02.1914
BRIEF [O.A.] Kluge Author: Kluge Recipient: Haeckel, Ernst Corporation: Brandenburgische Provinzialanstalt für Epileptische Dating: 12.01.1906
BRIEF [O.A.] Seiffert, Johannes Author: Seiffert, Johannes Recipient: Haeckel, Ernst Dating: 09.01.1880