BRIEF [O.A.] Steinmann, Gustav Author: Steinmann, Gustav Recipient: Haeckel, Ernst Dating: 09.03.1885
BRIEF [O.A.] Steinmann, Gustav Author: Steinmann, Gustav Recipient: Haeckel, Ernst Dating: 31.03.1885
BRIEF [O.A.] Steinmann, Gustav Author: Steinmann, Gustav Recipient: Haeckel, Ernst Dating: ??.03.1885
BRIEF [O.A.] Steinmann, Gustav Author: Steinmann, Gustav Recipient: Haeckel, Ernst Dating: 23.04.1885