BRIEF [O.A.] Pechuel-Loesche, Else Author: Pechuel-Loesche, Else Recipient: Haeckel, Ernst Dating: 09.06.1913
BRIEF [O.A.] Wachendorff, Theodor Author: Wachendorff, Theodor Recipient: Haeckel, Ernst Corporation: Deutscher Monistenbund, Ortsgruppe München Dating: 14.02.1913
TELEGRAMM Recipient: Haeckel, Ernst Corporation: Vorstand des Deutschen Monistenbundes Dating: 15.02.1913
POSTKARTE Semon, Richard W... Author: Semon, Richard W... Recipient: Haeckel, Ernst Dating: 15.01.1913
POSTKARTE Semon, Richard W... Author: Semon, Richard W... Recipient: Haeckel, Ernst Dating: 14.02.1913