BRIEF [O.A.] Freyer, Clemens Author: Freyer, Clemens Recipient: Haeckel, Ernst Corporation: Berliner Literarisches Auskunfts-Bureau Dating: 10.08.1892
BRIEF [O.A.] Freyer, Clemens Author: Freyer, Clemens Recipient: Haeckel, Ernst Corporation: Berliner Literarisches Auskunfts-Bureau Dating: 12.09.1892
BRIEF [O.A.] Fleischmann, Albert Author: Fleischmann, Albert Recipient: Haeckel, Ernst Dating: 17.02.1892
BRIEF [O.A.] Gizycki, Georg von Author: Gizycki, Georg von Recipient: Haeckel, Ernst Dating: 24.11.1892