BRIEF [O.A.] Böhtlingk, Arthur Author: Böhtlingk, Arthur Recipient: Haeckel, Ernst Dating: 17.09.1891
BRIEF [O.A.] Böhtlingk, Arthur Author: Böhtlingk, Arthur Recipient: Haeckel, Ernst Dating: 07.10.1891
BRIEF [O.A.] Kellogg, Vernon Lyman Author: Kellogg, Vernon Lyman Recipient: Haeckel, Ernst Corporation: Leland Stanford University Dating: ??.12.1894
BRIEF [O.A.] Kellogg, Vernon Lyman Author: Kellogg, Vernon Lyman Recipient: Haeckel, Ernst Dating: 15.11.1908
