BRIEF [O.A.] Kretschmer, Otto Author: Kretschmer, Otto Recipient: Haeckel, Ernst Corporation: Schlesische Zeitung Dating: 19.08.1908
BRIEF [O.A.] Müller, Max Author: Müller, Max Recipient: Haeckel, Ernst Corporation: J. U. Kern`s Verlag Dating: 03.07.1869
BRIEF [O.A.] Müller, Max Author: Müller, Max Recipient: Haeckel, Ernst Corporation: J. U. Kern`s Verlag Dating: 02.11.1871
