BRIEF [O.A.] Basso, Fritzi von Author: Basso, Fritzi von Recipient: Haeckel, Ernst Dating: 03.06.1909
BRIEF [O.A.] Basso, Fritzi von Author: Basso, Fritzi von Recipient: Haeckel, Ernst Dating: 23.05.1911(?)
BRIEF [O.A.] Basso, Fritzi von Author: Basso, Fritzi von Recipient: Haeckel, Ernst Dating: 07.07.1913