KARTE Maurer, Friedrich; Maurer, Marie Author: Maurer, Friedrich; Maurer, Marie Recipient: Haeckel, Ernst Dating: 16.02.1912
KARTE Lehmann-Russbüldt, Otto Author: Lehmann-Russbüldt, Otto Recipient: Haeckel, Ernst Corporation: Komitee Konfessionslos Dating: 15.02.1912