BRIEF [O.A.] Dybowski, Benedykt Author: Dybowski, Benedykt Recipient: Haeckel, Ernst Dating: 28.05.1901
BRIEF [O.A.] Dybowski, Benedykt Author: Dybowski, Benedykt Recipient: Haeckel, Ernst Dating: 30.03.1902
BRIEF [O.A.] Dybowski, Benedykt Author: Dybowski, Benedykt Recipient: Haeckel, Ernst Dating: 17.04.1902
BRIEF [O.A.] Czerski, Stanislaw Author: Czerski, Stanislaw Recipient: Haeckel, Ernst Corporation: Akademickie Kólko Przyrodników we Lwowie, Czytelnia Akademicka Dating: 03.01.1904
BRIEF [O.A.] Czarnecki, Johann Author: Czarnecki, Johann Recipient: Haeckel, Ernst Dating: 15.04.1871
BRIEF [O.A.] Czarnecki, Johann Author: Czarnecki, Johann Recipient: Haeckel, Ernst Dating: 01.08.1871
BRIEF [O.A.] Czarnecki, Johann Author: Czarnecki, Johann Recipient: Haeckel, Ernst Dating: 24.10.1871
BRIEF MIT UMSCHLAG Ernst [Prinz von Sachsen-Meiningen] Author: Ernst [Prinz von Sachsen-Meiningen] Recipient: Haeckel, Ernst Dating: 03.05.1917
BRIEF [O.A.] Grünspan, Therese Author: Grünspan, Therese Recipient: Haeckel, Ernst Dating: ??.02.1906