BRIEF [O.A.] Keller-Leuzinger, Franz Author: Keller-Leuzinger, Franz Recipient: Haeckel, Ernst Dating: 11.08.1881
BRIEF [O.A.] Kürschner, Joseph Author: Kürschner, Joseph Recipient: Haeckel, Ernst Corporation: W. Spemann, Verlagsbuchhandlung Dating: 09.05.1881
BRIEF [O.A.] Kürschner, Joseph Author: Kürschner, Joseph Recipient: Haeckel, Ernst Corporation: W. Spemann Verlagsbuchhandlung Dating: 29.03.1881
BRIEF [O.A.] Kürschner, Joseph Author: Kürschner, Joseph Recipient: Haeckel, Ernst Corporation: W. Spemann Verlagsbuchhandlung Dating: 19.04.1881