BRIEF [O.A.] Harden, Maximilian Author: Harden, Maximilian Recipient: Haeckel, Ernst Corporation: Die Zukunft Dating: 05.01.1893
BRIEF [O.A.] Harden, Maximilian Author: Harden, Maximilian Recipient: Haeckel, Ernst Corporation: Die Zukunft Dating: 27.04.1893
BRIEF [O.A.] Martens, Eduard von Author: Martens, Eduard von Recipient: Haeckel, Ernst Dating: 02.11.1893
BRIEF [O.A.] Semon, Richard Wolfgang Author: Semon, Richard Wolfgang Recipient: Haeckel, Ernst Dating: 02.05.1893