BRIEF [O.A.] Frapau-Akunian, Ilse Author: Frapau-Akunian, Ilse Recipient: Haeckel, Ernst Dating: 16.05.1903
BRIEF [O.A.] Gutmann, Herm... A... Author: Gutmann, Herm... A... Recipient: Haeckel, Ernst Dating: 24.05.1903
BRIEF [O.A.] Michaelsen, W... Author: Michaelsen, W... Recipient: Haeckel, Ernst Corporation: Naturhistorisches Museum Dating: 26.04.1903