POSTKARTE Basso, Fritzi von Author: Basso, Fritzi von Recipient: Haeckel, Ernst Dating: 15.10.1910(?)
POSTKARTE Bölsche, Wilhelm; Bölsche, Johanna Author: Bölsche, Wilhelm; Bölsche, Johanna Recipient: Haeckel, Ernst Dating: 13.06.1910
POSTKARTE Bölsche, Wilhelm; Bölsche, Johanna Author: Bölsche, Wilhelm; Bölsche, Johanna Recipient: Haeckel, Ernst Dating: 25.06.1910