BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 31.03.1901
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 05.01.1902
POSTKARTE Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 19.02.1902
POSTKARTE Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 19.02.1903
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 15.02.1905
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 23.02.1905
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 15.02.1906
POSTKARTE Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 12.11.1906
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 15.02.1907
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 15.02.1908