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