BRIEF OHNE UMSCHLAG Erdmann, Gustav Adolf Author: Erdmann, Gustav Adolf Recipient: Haeckel, Ernst Dating: 15.02.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 19.05.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 27.05.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 19.08.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 19.09.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 19.11.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 01.12.1889
BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: ??.??.1889