BRIEF OHNE UMSCHLAG Berini, Julius Ferdinand Author: Berini, Julius Ferdinand Recipient: Haeckel, Ernst Dating: 25.05.1874
BRIEF [O.A.] Keller, Walther Author: Keller, Walther Recipient: Haeckel, Ernst Corporation: Franckh'sche Verlagshandlung Dating: 08.07.1913
BRIEF [O.A.] Keller-Leuzinger, Franz Author: Keller-Leuzinger, Franz Recipient: Haeckel, Ernst Dating: 11.08.1881
BRIEF [O.A.] Keller-Leuzinger, Franz Author: Keller-Leuzinger, Franz Recipient: Haeckel, Ernst Dating: 08.01.1882
BRIEF [O.A.] Keller-Leuzinger, Franz Author: Keller-Leuzinger, Franz Recipient: Haeckel, Ernst Dating: 12.01.1882
BRIEF [O.A.] Keller-Leuzinger, Franz Author: Keller-Leuzinger, Franz Recipient: Haeckel, Ernst Dating: 15.05.1882
BRIEF [O.A.] Keller-Leuzinger, Franz Author: Keller-Leuzinger, Franz Recipient: Haeckel, Ernst Dating: 15.06.1882
