BRIEF [O.A.] Foerster, Wilhelm Author: Foerster, Wilhelm Recipient: Haeckel, Ernst Dating: 15.05.1889
POSTKARTE Blochmann, Friedrich Author: Blochmann, Friedrich Recipient: Haeckel, Ernst Dating: 15.05.1903
BRIEF [O.A.] Blochmann, Friedrich Author: Blochmann, Friedrich Recipient: Haeckel, Ernst Corporation: Zoologisches Institut der Universität Dating: 14.02.1904
POSTKARTE Blochmann, Friedrich Author: Blochmann, Friedrich Recipient: Haeckel, Ernst Dating: 27.05.1904
BRIEF [O.A.] Blochmann, Friedrich Author: Blochmann, Friedrich Recipient: Haeckel, Ernst Dating: 04.03.1911