BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 24.04.1914
BRIEF [O.A.] Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 16.05.1914
TELEGRAMM Kleinsorgen, Wilhelm Author: Kleinsorgen, Wilhelm Recipient: Haeckel, Ernst Dating: 16.02.1914