TELEGRAMM Vertongen, Lucien Author: Vertongen, Lucien Recipient: Haeckel, Ernst Corporation: Libre Pensée de Bruxelles Dating: 14.01.1912
TELEGRAMM Sethe-Seyberth, Louise; Sethe, Walter Author: Sethe-Seyberth, Louise; Sethe, Walter Recipient: Haeckel, Ernst Dating: 15.02.1914
TELEGRAMM Sethe-Seyberth, Luise Author: Sethe-Seyberth, Luise Recipient: Haeckel, Ernst Dating: 19.02.1904