BRIEF [O.A.] Theszóll, Charles Author: Theszóll, Charles Recipient: Haeckel, Ernst Dating: 23-02-1900
BRIEF [O.A.] Feichtinger, Alexius Baron Author: Feichtinger, Alexius Baron Recipient: Haeckel, Ernst Dating: 09.02.1914
BRIEF [O.A.] Rozsnyay, Calman von Author: Rozsnyay, Calman von Recipient: Haeckel, Ernst Dating: 14.03.1917