BRIEF [O.A.] Auerbach, Leopold Author: Auerbach, Leopold Recipient: Haeckel, Ernst Dating: 18.01.1874
BRIEF [O.A.] Auerbach, Leopold Author: Auerbach, Leopold Recipient: Haeckel, Ernst Dating: 01.11.1882
BRIEF [O.A.] Auerbach, Leopold Author: Auerbach, Leopold Recipient: Haeckel, Ernst Dating: 16.02.1894
BRIEF [O.A.] Barret-Lennard, M... Author: Barret-Lennard, M... Recipient: Haeckel, Ernst Dating: 19.01.????
BRIEF [O.A.] Baader, F... A... Author: Baader, F... A... Recipient: Haeckel, Ernst Corporation: Reichsstickstoff-Werke Dating: 07.03.1917