BRIEF [O.A.] Hasse, Johann Carl Author: Hasse, Johann Carl Recipient: Haeckel, Ernst Dating: 15.01.1894
BRIEF [O.A.] Hasse, Johann Carl Author: Hasse, Johann Carl Recipient: Haeckel, Ernst Dating: 19.03.1894
BRIEF [O.A.] Hasse, Johann Carl Author: Hasse, Johann Carl Recipient: Haeckel, Ernst Dating: 21.06.1894
BRIEF [O.A.] Hasse, Johann Carl Author: Hasse, Johann Carl Recipient: Haeckel, Ernst Dating: 12.08.1894
BRIEF [O.A.] Auerbach, Leopold Author: Auerbach, Leopold Recipient: Haeckel, Ernst Dating: 16.02.1894