POSTKARTE Becker, Franz Johann Jakob Emil Author: Becker, Franz Johann Jakob Emil Recipient: Haeckel, Ernst Dating: 11.04.1918
BRIEF OHNE UMSCHLAG Becker, Franz Johann Jakob Emil Author: Becker, Franz Johann Jakob Emil Recipient: Haeckel, Ernst Dating: 16.11.1918
BRIEF OHNE UMSCHLAG Almeroth, Hans Author: Almeroth, Hans Recipient: Haeckel, Ernst Dating: 11.02.1918
BRIEF [O.A.] Schoeller, Eugenie Author: Schoeller, Eugenie Recipient: Haeckel, Ernst Dating: 28.04.1918
BRIEF [O.A.] Schaufenbühl, Friedrich Author: Schaufenbühl, Friedrich Recipient: Haeckel, Ernst Dating: 17.08.1918