BRIEF OHNE UMSCHLAG Keller, Conrad Author: Keller, Conrad Recipient: Haeckel, Ernst Dating: 29.06.1881
BRIEF [O.A.] Zolling, Theophil Author: Zolling, Theophil Recipient: Haeckel, Ernst Corporation: Die Gegenwart Dating: 18.08.1881
BRIEF OHNE UMSCHLAG Haeckel, Agnes; Haeckel, Ernst Author: Haeckel, Agnes; Haeckel, Ernst Recipient: Niess, Albert Dating: 30.08.1881