BRIEF [O.A.] Jankelowitz, Adolf Author: Jankelowitz, Adolf Recipient: Haeckel, Ernst Dating: 12.03.1904
BRIEF [O.A.] Jankelowitz, Adolf Author: Jankelowitz, Adolf Recipient: Haeckel, Ernst Dating: 05.11.1904
BRIEF [O.A.] Metzner, Heinrich Author: Metzner, Heinrich Recipient: Haeckel, Ernst Dating: 15.02.1904
BRIEF [O.A.] Koehler, Woldemar Author: Koehler, Woldemar Recipient: Haeckel, Ernst Dating: 23.08.1904