BRIEF [O.A.] Spengel, J... W... Author: Spengel, J... W... Recipient: Haeckel, Ernst Dating: 14.11.1896
BRIEF [O.A.] Spengel, J... W... Author: Spengel, J... W... Recipient: Haeckel, Ernst Dating: 04.07.1916
BRIEF [O.A.] Roth, Emil Author: Roth, Emil Recipient: Haeckel, Ernst Corporation: Verlags- und Kunstbuchhandlung Dating: 25.11.1899
BRIEF [O.A.] Roth, Emil Author: Roth, Emil Recipient: Haeckel, Ernst Corporation: Verlags- und Kunstbuchhandlung Dating: 06.07.1906
BRIEF OHNE UMSCHLAG Leuckart, Rudolf Author: Leuckart, Rudolf Recipient: Haeckel, Ernst Dating: 28.05.1865