POSTKARTE Osborn, Henry Fairfield Author: Osborn, Henry Fairfield Recipient: Haeckel, Ernst Dating: ??.??.1906
POSTKARTE Calenda, Vincent D. Author: Calenda, Vincent D. Recipient: Haeckel, Ernst Dating: 24.12.1913
POSTKARTE Voelckel, C... B... Author: Voelckel, C... B... Recipient: Haeckel, Ernst Dating: 03.10.1914