BRIEF [O.A.] Ercolani, G... B... Author: Ercolani, G... B... Recipient: Haeckel, Ernst Dating: 18.02.1877
BRIEF [O.A.] Siciliani, Pietro Author: Siciliani, Pietro Recipient: Haeckel, Ernst Dating: 07.02.1877
BRIEF [O.A.] Siciliani, Pietro Author: Siciliani, Pietro Recipient: Haeckel, Ernst Dating: 18.02.1877