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: 21.04.1909
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 23.12.1915
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 31.05.1916