BRIEF [O.A.] Lilienthal, Friedrich Wilhelm Author: Lilienthal, Friedrich Wilhelm Recipient: Haeckel, Ernst Dating: 02.02.1904
BRIEF [O.A.] Ward, Lester Frank Author: Ward, Lester Frank Recipient: Haeckel, Ernst Dating: 11.11.1904
BRIEF [O.A.] Birkhahn, Robert C. Author: Birkhahn, Robert C. Recipient: Haeckel, Ernst Dating: 13.01.1904