BRIEF [O.A.] Gutmann, Herm... A... Author: Gutmann, Herm... A... Recipient: Haeckel, Ernst Dating: 01.01.1907
BRIEF [O.A.] Gutmann, Herm... A... Author: Gutmann, Herm... A... Recipient: Haeckel, Ernst Dating: 24.09.1907
BRIEF [O.A.] Gutmann, Herm... A... Author: Gutmann, Herm... A... Recipient: Haeckel, Ernst Dating: 09.10.1907