BRIEF [O.A.] Duplay, Geo... F... Author: Duplay, Geo... F... Recipient: Haeckel, Ernst Dating: 30.11.1904
BRIEF [O.A.] Duplay, Geo... F... Author: Duplay, Geo... F... Recipient: Haeckel, Ernst Dating: 28.12.1904
BRIEF [O.A.] Duplay, Geo... F... Author: Duplay, Geo... F... Recipient: Haeckel, Ernst Dating: 09.04.1905