BRIEF [O.A.] Lewinsky, Bernhard Author: Lewinsky, Bernhard Recipient: Haeckel, Ernst Dating: 15.02.1914
BRIEF [O.A.] Haeckel, Heinrich Author: Haeckel, Heinrich Recipient: Haeckel, Ernst Dating: 08.08.1914
BRIEF [O.A.] Enderlein, Günther Author: Enderlein, Günther Recipient: Haeckel, Ernst Dating: 15.02.1914