BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 31.05.1916
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 25.10.1916
BRIEF [O.A.] Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 05.11.1916
BRIEF OHNE UMSCHLAG Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Schmidt, Heinrich Dating: 27.02.1916
BRIEF OHNE UMSCHLAG Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 20.07.1916
BILDPOSTKARTE Ludowici, Wilhelm Author: Ludowici, Wilhelm Recipient: Haeckel, Ernst Dating: 22.05.1916