BRIEF [O.A.] Vierordt, Heinrich Author: Vierordt, Heinrich Recipient: Haeckel, Ernst Dating: 03.12.1899
BRIEF [O.A.] Vierordt, Heinrich Author: Vierordt, Heinrich Recipient: Haeckel, Ernst Dating: 30.11.1899
BRIEF [O.A.] Vierordt, Heinrich Author: Vierordt, Heinrich Recipient: Haeckel, Ernst Dating: 16.11.1899