BRIEF [O.A.] Bibaud, J... J... E... Author: Bibaud, J... J... E... Recipient: Haeckel, Ernst Dating: 23.07.1911
BRIEF [O.A.] Bibaud, J... J... E... Author: Bibaud, J... J... E... Recipient: Haeckel, Ernst Dating: 14.09.1912
BRIEF [O.A.] Bibaud, J... J... E... Author: Bibaud, J... J... E... Recipient: Haeckel, Ernst Dating: 25.12.1914