POSTKARTE Geißler, Felix Author: Geißler, Felix Recipient: Haeckel, Ernst Corporation: Alfred Kröner Verlag Stuttgart Dating: 17.10.1918
POSTKARTE Hiersemann, Karl W. Author: Hiersemann, Karl W. Recipient: Haeckel, Walther Dating: 21.12.1917
POSTKARTE Recipient: Palmén, Johan Axel Corporation: Bibliographisches Institut Leipzig Dating: 05.06.1899