BRIEF [O.A.] Schoeller, Eugenie Author: Schoeller, Eugenie Recipient: Haeckel, Ernst Dating: 24.01.1916
BRIEF [O.A.] Schoeller, Eugenie Author: Schoeller, Eugenie Recipient: Haeckel, Ernst Dating: 18.06.1916
POSTKARTE Schuster, Adolf Niklaus Author: Schuster, Adolf Niklaus Recipient: Haeckel, Ernst Dating: 16.02.1916
BRIEF OHNE UMSCHLAG Sarasin, Fritz Author: Sarasin, Fritz Recipient: Haeckel, Ernst Dating: 29.10.1916