BRIEF [O.A.] Hubrecht, Ambrosius A... W... Author: Hubrecht, Ambrosius A... W... Recipient: Haeckel, Ernst Dating: 16.06.1878
BRIEF [O.A.] Vitringa, Anne Johan Author: Vitringa, Anne Johan Recipient: Haeckel, Ernst Dating: 25.02.1878
BRIEF [O.A.] Koch, M... Author: Koch, M... Recipient: Haeckel, Ernst Corporation: Koch & Vlierboom Dating: 07.10.1878