BRIEF [O.A.] Schmidt, Heinrich Author: Schmidt, Heinrich Recipient: Haeckel, Ernst Dating: 23.01.1916
BRIEF OHNE UMSCHLAG Schmidt, Heinrich Author: Schmidt, Heinrich Recipient: Haeckel, Ernst Dating: 25.07.1916
BRIEF OHNE UMSCHLAG Schmidt, Heinrich Author: Schmidt, Heinrich Recipient: Haeckel, Ernst Dating: 28.06.1916
BRIEF OHNE UMSCHLAG Schmidt, Heinrich Author: Schmidt, Heinrich Recipient: Haeckel, Ernst Dating: 30.09.1916