BRIEFENTWURF Eggeling, Heinrich Author: Eggeling, Heinrich Recipient: Haeckel, Ernst Dating: 04.06.1908
BRIEFENTWURF Eggeling, Heinrich von Author: Eggeling, Heinrich von Recipient: Haeckel, Ernst Dating: 21.02.1907
BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Monaco, Albert I. Fürst von Dating: 08.12.1908
BRIEFENTWURF Breitenbach, Wilhelm Author: Breitenbach, Wilhelm Recipient: Haeckel, Ernst Dating: 27.11.1916
BRIEFENTWURF Sprenger, Therese Author: Sprenger, Therese Recipient: Haeckel, Ernst Dating: 23.12.1912