BRIEF [O.A.] Eggeling, Heinrich von Author: Eggeling, Heinrich von Recipient: Haeckel, Ernst Dating: 20.10.1901
BRIEF OHNE UMSCHLAG Escherich, Karl Leopold Author: Escherich, Karl Leopold Recipient: Haeckel, Ernst Dating: 26.06.1901
BRIEF OHNE UMSCHLAG Escherich, Karl Leopold Author: Escherich, Karl Leopold Recipient: Haeckel, Ernst Dating: 20.07.1901
BRIEF [O.A.] Goette, Alexander Author: Goette, Alexander Recipient: Haeckel, Ernst Dating: 28.02.1875