BRIEF [O.A.] Hoffmann-Kutschek, Arthur Author: Hoffmann-Kutschek, Arthur Recipient: Haeckel, Ernst Dating: 10.10.1905
BRIEF [O.A.] Hübner, Max und Maria [?] Author: Hübner, Max und Maria [?] Recipient: Haeckel, Ernst Dating: 24.11.1905