BRIEF OHNE UMSCHLAG Radonetz, Eduard Author: Radonetz, Eduard Recipient: Haeckel, Ernst Dating: 01.12.1885
BRIEF [O.A.] Krauseneck, Gustav Author: Krauseneck, Gustav Recipient: Haeckel, Ernst Dating: 27.08.1919
BRIEF OHNE UMSCHLAG Hatschek, Berthold Author: Hatschek, Berthold Recipient: Haeckel, Ernst Dating: 09.07.1891
BRIEF [O.A.] Pascotini, B... Carl Author: Pascotini, B... Carl Recipient: Haeckel, Ernst Dating: 10.01.1873