BRIEF OHNE UMSCHLAG Schleußner, Otto Author: Schleußner, Otto Recipient: Haeckel, Ernst Dating: 16.07.1904
BRIEF [O.A.] Vogt, Johann Gustav Author: Vogt, Johann Gustav Recipient: Haeckel, Ernst Dating: 12.03.1904
BRIEF [O.A.] Vogt, Johann Gustav Author: Vogt, Johann Gustav Recipient: Haeckel, Ernst Dating: 23.05.1904
BRIEF [O.A.] Vogt, Johann Gustav Author: Vogt, Johann Gustav Recipient: Haeckel, Ernst Dating: 10.06.1904
BRIEF [O.A.] Vogt, Johann Gustav Author: Vogt, Johann Gustav Recipient: Haeckel, Ernst Dating: 23.12.1904
BRIEF [O.A.] Ratzel, Friedrich Author: Ratzel, Friedrich Recipient: Haeckel, Ernst Dating: 14.02.1904