BILDPOSTKARTE Meyer, Gertrud und Else Author: Meyer, Gertrud und Else Recipient: Haeckel, Ernst Dating: 31.12.1905
BRIEF [O.A.] Engelmann, Wilhelm A... Author: Engelmann, Wilhelm A... Recipient: Haeckel, Ernst Dating: 25.07.1905
BRIEF [O.A.] Engelmann, Friedrich Author: Engelmann, Friedrich Recipient: Haeckel, Ernst Corporation: Friedrich Engelmann Verlagsbuchhandlung Dating: 30.11.1905
BRIEF [O.A.] Engelmann, Friedrich Author: Engelmann, Friedrich Recipient: Haeckel, Ernst Corporation: Friedrich Engelmann Verlagsbuchhandlung Dating: 12.12.1905