BRIEF [O.A.] Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 01.02.1915
BRIEF [O.A.] Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 13.02.1915
BRIEF [O.A.] Juliusburger, Otto Author: Juliusburger, Otto Recipient: Haeckel, Ernst Dating: 19.12.1915