BRIEF MIT UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Bölsche, Wilhelm Dating: 06.01.1915
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Bölsche, Wilhelm Dating: 30.04.1904
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Charlotte Dating: 09.05.1880