BRIEF OHNE UMSCHLAG Hatschek, Berthold Author: Hatschek, Berthold Recipient: Haeckel, Ernst Dating: 19.09.1910
BRIEF OHNE UMSCHLAG Hatschek, Berthold Author: Hatschek, Berthold Recipient: Haeckel, Ernst Dating: 10.10.1910
BRIEF [O.A.] Hatschek, Berthold Author: Hatschek, Berthold Recipient: Haeckel, Ernst Dating: 28.11.1910