POSTKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Haeckel, Ernst Dating: 1904.??.?? - 1905.??.??
TELEGRAMM Grazie, Marie Eugenie delle; Müllner, Laurenz Author: Grazie, Marie Eugenie delle; Müllner, Laurenz Recipient: Haeckel, Ernst Dating: 15.02.1904
ANSICHTSKARTE Grazie, Marie Eugenie delle; Müllner, Laurenz Author: Grazie, Marie Eugenie delle; Müllner, Laurenz Recipient: Haeckel, Ernst Dating: 19.08.1904
BRIEF [O.A.] Gümbel, C... Godfrey Author: Gümbel, C... Godfrey Recipient: Haeckel, Ernst Dating: 23.02.1904
BRIEF [O.A.] Fernbach, Wolfgang Author: Fernbach, Wolfgang Recipient: Haeckel, Ernst Dating: 16.02.1904