POSTKARTE Becker, Franz Johann Jakob Emil Author: Becker, Franz Johann Jakob Emil Recipient: Haeckel, Ernst Dating: 15.07.1914
POSTKARTE Just, ? Author: Just, ? Recipient: Haeckel, Ernst Corporation: Institut Concordia Dating: 25.10.1914
POSTKARTE Bischoff, Gottfried Author: Bischoff, Gottfried Recipient: Haeckel, Ernst Dating: 16.02.1914