BRIEF [O.A.] Recipient: Haeckel, Ernst Corporation: Bibliothèque Nationale Ottomane Dating: 18.03.1911
BRIEF [O.A.] Recipient: Haeckel, Ernst Corporation: Bibliothèque Nationale Ottomane Dating: 07.04.1911
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Charlotte Dating: 13.04.1873
BRIEF [O.A.] Cogevina, Nicolaus Author: Cogevina, Nicolaus Recipient: Haeckel, Ernst Dating: 23.08.1877
BRIEF [O.A.] Cogevina, Nicolaus Author: Cogevina, Nicolaus Recipient: Haeckel, Ernst Dating: 17.09.1877
BRIEF [O.A.] Délyanny, Théodore Author: Délyanny, Théodore Recipient: Haeckel, Ernst Dating: 21.06.1896