BRIEF [O.A.] Wyhe, Jan Willem van Author: Wyhe, Jan Willem van Recipient: Haeckel, Ernst Dating: 26.11.1886
BRIEF [O.A.] Wyhe, Jan Willem van Author: Wyhe, Jan Willem van Recipient: Haeckel, Ernst Dating: 15.11.1891
BRIEF [O.A.] Wyhe, Jan Willem van Author: Wyhe, Jan Willem van Recipient: Haeckel, Ernst Dating: 28.10.1895