BRIEF [O.A.] Stern, Maximilian L. Author: Stern, Maximilian L. Recipient: Haeckel, Ernst Dating: 07.03.1875
BRIEF [O.A.] Bäumler, Johann Andreas Author: Bäumler, Johann Andreas Recipient: Haeckel, Ernst Dating: 13.04.1878
BRIEF [O.A.] Bäumler, Johann Andreas Author: Bäumler, Johann Andreas Recipient: Haeckel, Ernst Dating: 24.10.1878
BRIEF [O.A.] Bäumler, Johann Andreas Author: Bäumler, Johann Andreas Recipient: Haeckel, Ernst Dating: 13.02.1909