BRIEF [O.A.] Ortmann, Arnold E... Author: Ortmann, Arnold E... Recipient: Haeckel, Ernst Dating: 17.06.1887
BRIEF [O.A.] Ortmann, Arnold E... Author: Ortmann, Arnold E... Recipient: Haeckel, Ernst Dating: 01.05.1888
BRIEF [O.A.] Ortmann, Arnold E... Author: Ortmann, Arnold E... Recipient: Haeckel, Ernst Dating: 25.09.1890
BRIEF [O.A.] Ortmann, Arnold E... Author: Ortmann, Arnold E... Recipient: Haeckel, Ernst Dating: 07.02.1891
BRIEF [O.A.] Pfrang, Friedrich Author: Pfrang, Friedrich Recipient: Haeckel, Ernst Dating: 15.02.1914
BRIEF [O.A.] Ortmann, Arnold E... Author: Ortmann, Arnold E... Recipient: Haeckel, Ernst Dating: 16.03.1894