BRIEF [O.A.] Vertongen, Lucien Author: Vertongen, Lucien Recipient: Haeckel, Ernst Corporation: Libre Pensée de Bruxelles Dating: 09.11.1912
TELEGRAMM Vertongen, Lucien Author: Vertongen, Lucien Recipient: Haeckel, Ernst Corporation: Libre Pensée de Bruxelles Dating: 14.01.1912
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 26.10.1889
BRIEF [O.A.] Recipient: Haeckel, Ernst Corporation: Académie Royale des Sciences, des Lettres ...Bruxelles Dating: 15.12.1897
BRIEF [O.A.] Kemna, Adolf Author: Kemna, Adolf Recipient: Haeckel, Ernst Corporation: Antwerp Waterworks Company Limited Dating: 16.03.1894
