BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 01.11.1918
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 02.02.1919
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 13.05.1919
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 06.07.1906