BRIEF [O.A.] Hasse, Johann Carl Author: Hasse, Johann Carl Recipient: Haeckel, Ernst Dating: 20.12.1873
BRIEF [O.A.] Masłowski, Ludwik Author: Masłowski, Ludwik Recipient: Haeckel, Ernst Corporation: Redakcja Biblioteki Umiejetnosci przyrodniczych Dating: 19.02.1873
BRIEF [O.A.] Nowicki, Maximilian Author: Nowicki, Maximilian Recipient: Haeckel, Ernst Dating: 18.01.1873
BRIEF [O.A.] Nowicki, Maximilian Author: Nowicki, Maximilian Recipient: Haeckel, Ernst Dating: 19.12.1873