BRIEF OHNE UMSCHLAG Spreer, Leopold Author: Spreer, Leopold Recipient: Haeckel, Ernst Dating: 17.08.1906
BRIEF OHNE UMSCHLAG Thielemann, Heinrich Author: Thielemann, Heinrich Recipient: Haeckel, Ernst Dating: 24.04.1865
BRIEF OHNE UMSCHLAG Thielemann, Heinrich Author: Thielemann, Heinrich Recipient: Haeckel, Ernst Dating: 11.07.1867
BRIEF OHNE UMSCHLAG Thielemann, Heinrich Author: Thielemann, Heinrich Recipient: Haeckel, Ernst Dating: 31.05.1875
BRIEF [O.A.] Thielemann, Ernst Author: Thielemann, Ernst Recipient: Haeckel, Ernst Dating: 29.05.1876