POSTKARTE Stanezewski, Johann Author: Stanezewski, Johann Recipient: Haeckel, Ernst Dating: 27.05.1912
TELEGRAMM Steinthal, Walter Author: Steinthal, Walter Recipient: Haeckel, Ernst Corporation: Deutsche Montagszeitung Dating: 03.02.1912
BRIEF MIT UMSCHLAG Brandt, Oscar Ludwig Author: Brandt, Oscar Ludwig Recipient: Haeckel, Ernst Dating: 13.07.1912