BRIEF [O.A.] Gutmann, Herm... A... Author: Gutmann, Herm... A... Recipient: Haeckel, Ernst Dating: 12.02.1904
POSTKARTE Recipient: Haeckel, Ernst Corporation: August Blumenthal, Transitus – Hamburg Dating: 01.07.1904
BRIEF [O.A.] Harms, Adolf Author: Harms, Adolf Recipient: Haeckel, Ernst Corporation: Carl Harms Weinhandlung Dating: 16.02.1904
BRIEF [O.A.] Unna, P...(aul) G...(erson) Author: Unna, P...(aul) G...(erson) Recipient: Haeckel, Ernst Dating: 24.02.1904