BRIEF OHNE UMSCHLAG Mieglus, L. [et al.] Author: Mieglus, L. [et al.] Recipient: Haeckel, Ernst Dating: 14.02.1909
BRIEF OHNE UMSCHLAG Heske, Franz [et al.] Author: Heske, Franz [et al.] Recipient: Haeckel, Ernst Dating: 1909.02.?? [?]
BRIEF OHNE UMSCHLAG Söllner, H. Author: Söllner, H. Recipient: Haeckel, Ernst Dating: 1909.02.?? [ca.]