BRIEF [O.A.] Weidenmüller. Joh... Author: Weidenmüller. Joh... Recipient: Haeckel, Ernst Corporation: Leipziger Freie Studentenschaft Dating: 23.06.1905
BRIEF [O.A.] John, Elisabeth Author: John, Elisabeth Recipient: Haeckel, Ernst Corporation: Lagerei-Berufsgenossenschaft, Sektion IX Dating: 29.04.1905
BRIEF OHNE UMSCHLAG Bornemann, Edmund Author: Bornemann, Edmund Recipient: Haeckel, Ernst Dating: 11.08.1905
BRIEF [O.A.] Engelmann, Wilhelm A... Author: Engelmann, Wilhelm A... Recipient: Haeckel, Ernst Dating: 25.07.1905
BRIEF [O.A.] Engelmann, Friedrich Author: Engelmann, Friedrich Recipient: Haeckel, Ernst Corporation: Friedrich Engelmann Verlagsbuchhandlung Dating: 30.11.1905