ANSICHTSKARTE Hielscher, Heinrich Author: Hielscher, Heinrich Recipient: Haeckel, Ernst Dating: 15.02.1914
ANSICHTSKARTE Wiggert, Friedrich Author: Wiggert, Friedrich Recipient: Haeckel, Ernst Dating: 15.02.1909
ANSICHTSKARTE Maurer, Friedrich Author: Maurer, Friedrich Recipient: Haeckel, Ernst Dating: 18.04.1915