BRIEF [O.A.] Preyer, William Thierry Author: Preyer, William Thierry Recipient: Haeckel, Ernst Dating: 21.10.1872
BRIEF [O.A.] Kupffer, Carl Wilhelm von Author: Kupffer, Carl Wilhelm von Recipient: Haeckel, Ernst Dating: 21.02.1872
BRIEF [O.A.] Koch, Eduard Author: Koch, Eduard Recipient: Haeckel, Ernst Corporation: E. Schweizerbart`sche Verlagsbuchhandlung, Eduard Koch Dating: 08.12.1872