BRIEF [O.A.] Bibaud, J... J... E... Author: Bibaud, J... J... E... Recipient: Haeckel, Ernst Dating: 23.07.1911
BRIEF [O.A.] Blochmann, Friedrich Author: Blochmann, Friedrich Recipient: Haeckel, Ernst Dating: 04.03.1911
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 [O.A.] Bennhill, Basil Author: Bennhill, Basil Recipient: Haeckel, Ernst Corporation: House of Representatives U. S. Dating: 07.10.1911