BRIEF [O.A.] Ziegler, Heinrich Ernst Author: Ziegler, Heinrich Ernst Recipient: Haeckel, Ernst Dating: 14.03.1900
BRIEF [O.A.] Jousset de Bellesme Author: Jousset de Bellesme Recipient: Haeckel, Ernst Dating: 21.01.1910
BRIEF [O.A.] Jousset de Bellesme Author: Jousset de Bellesme Recipient: Haeckel, Ernst Dating: 22.04.1912
BRIEF [O.A.] Sadeleer, C... F... de Author: Sadeleer, C... F... de Recipient: Haeckel, Ernst Dating: 23.07.1906