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 OHNE UMSCHLAG Berliner, Theodor Author: Berliner, Theodor Recipient: Haeckel, Ernst Dating: 23.07.1876