BRIEF [O.A.] Posendorfer, Victor Author: Posendorfer, Victor Recipient: Haeckel, Ernst Dating: 24.11.1910
BRIEF [O.A.] Lendenfeld, Robert von Author: Lendenfeld, Robert von Recipient: Haeckel, Ernst Corporation: Universität Innsbruck Dating: 20.10.1889
BRIEF [O.A.] Lendenfeld, Robert von Author: Lendenfeld, Robert von Recipient: Haeckel, Ernst Dating: 10.03.1892