BRIEF [O.A.] Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 02.08.1901
BRIEF OHNE UMSCHLAG Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 18.10.1914
BRIEF OHNE UMSCHLAG Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 11.11.1908
BRIEF [O.A.] Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 25.12.1910
BRIEF [O.A.] Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 26.02.1911