BRIEF [O.A.] Zacharias, Otto Author: Zacharias, Otto Recipient: Haeckel, Ernst Corporation: Zootom. Institut Dating: 07.07.1883
BRIEF [O.A.] Zacharias, Otto Author: Zacharias, Otto Recipient: Haeckel, Ernst Corporation: Privat-Laboratorium für mikroskopische und zootomische Untersuchungen Dating: 14.01.1885
BRIEF [O.A.] Zacharias, Otto Author: Zacharias, Otto Recipient: Haeckel, Ernst Corporation: Biologische Station Dating: 04.04.1898