BRIEF [O.A.] Doehler, Gottfried Author: Doehler, Gottfried Recipient: Haeckel, Ernst Dating: 24.07.1892
BRIEF [O.A.] Schneider, Friedrich Author: Schneider, Friedrich Recipient: Haeckel, Ernst Dating: 15.02.1911
BRIEF [O.A.] Schneider, Friedrich Author: Schneider, Friedrich Recipient: Haeckel, Ernst Dating: 17.02.1910
BRIEF [O.A.] Schloßmacher, Jos... Author: Schloßmacher, Jos... Recipient: Haeckel, Ernst Corporation: Redaktion der Greizer Zeitung Dating: 12.02.1897