POSTKARTE Bölsche, Wilhelm; Bölsche, Johanna Author: Bölsche, Wilhelm; Bölsche, Johanna Recipient: Haeckel, Ernst Dating: 01.06.1903
POSTKARTE Bölsche, Wilhelm; Bölsche, Johanna Author: Bölsche, Wilhelm; Bölsche, Johanna Recipient: Haeckel, Ernst Dating: 04.07.1903
BRIEF OHNE UMSCHLAG Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 22.08.1903
BRIEF [O.A.] Szarlitt, Bernard Author: Szarlitt, Bernard Recipient: Haeckel, Ernst Dating: 18.03.1903
BRIEF [O.A.] Schultz, Ehrenfried Author: Schultz, Ehrenfried Recipient: Haeckel, Ernst Dating: 26.07.1903