BRIEF [O.A.] Steman, Friedrich Author: Steman, Friedrich Recipient: Haeckel, Ernst Dating: 15.02.1917
BRIEF [O.A.] Steman, Friedrich Author: Steman, Friedrich Recipient: Haeckel, Ernst Dating: 06.03.1917
BRIEF [O.A.] Steman, Friedrich Author: Steman, Friedrich Recipient: Haeckel, Ernst Dating: 09.04.1917
BRIEF [O.A.] Steman, Friedrich Author: Steman, Friedrich Recipient: Haeckel, Ernst Dating: 27.05.1917
BRIEF [O.A.] Steman, Friedrich Author: Steman, Friedrich Recipient: Haeckel, Ernst Dating: 23.10.1917