BRIEF OHNE UMSCHLAG Radowanowic, Marinko Author: Radowanowic, Marinko Recipient: Haeckel, Ernst Dating: 28.11.1875
BRIEF [O.A.] Miljkoviel, Lubomir Author: Miljkoviel, Lubomir Recipient: Haeckel, Ernst Dating: 09.10.1877
BRIEF [O.A.] Miljkoviel, Lubomir Author: Miljkoviel, Lubomir Recipient: Haeckel, Ernst Dating: 01.01.1876
BRIEF OHNE UMSCHLAG Bibits, Sofie von Author: Bibits, Sofie von Recipient: Haeckel, Ernst Dating: 02.04.1914
TELEGRAMM Ivezic, Gerassim P. Author: Ivezic, Gerassim P. Recipient: Haeckel, Ernst Dating: 16.02.1909