ANSICHTSKARTE Bockelmann, Friedrich Author: Bockelmann, Friedrich Recipient: Haeckel, Ernst Dating: 03.03.1911
ANSICHTSKARTE Maurer, Friedrich Author: Maurer, Friedrich Recipient: Haeckel, Ernst Dating: 10.06.1911
ANSICHTSKARTE Haeckel, Ernst Franz Max Author: Haeckel, Ernst Franz Max Recipient: Haeckel, Ernst Dating: 15.02.1911