BRIEF OHNE UMSCHLAG Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 19.08.1902
BRIEF OHNE UMSCHLAG Bergner, Franz Author: Bergner, Franz Recipient: Haeckel, Ernst Dating: 25.04.1902
BRIEF OHNE UMSCHLAG Ellram, Arthur Author: Ellram, Arthur Recipient: Haeckel, Ernst Dating: 04.02.1902
BRIEF [O.A.] Haeckel, Heinrich Author: Haeckel, Heinrich Recipient: Haeckel, Ernst Dating: 15.06.1902
BRIEF [O.A.] Haeckel, Heinrich Author: Haeckel, Heinrich Recipient: Haeckel, Ernst Dating: 15.02.1902