BRIEF [O.A.] Schwaike, Wilhelm Author: Schwaike, Wilhelm Recipient: Haeckel, Ernst Dating: 08.08.1886
BRIEF [O.A.] Schwaike, Wilhelm Author: Schwaike, Wilhelm Recipient: Haeckel, Ernst Dating: 14.02.1886
BRIEF [O.A.] Krug, Max Author: Krug, Max Recipient: Haeckel, Ernst Corporation: Max Krug & Co. Dating: 17.04.1886