BRIEF OHNE UMSCHLAG Korsch, Carl August Author: Korsch, Carl August Recipient: Haeckel, Ernst Dating: 27.12.1900
BRIEF OHNE UMSCHLAG Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 18.01.1900
BRIEF OHNE UMSCHLAG Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 03.03.1900