BRIEF [O.A.] Waldthausen, J... von [?] Author: Waldthausen, J... von [?] Recipient: Haeckel, Ernst Dating: 10.03.1907
BRIEF [O.A.] Waldthausen, J... von Author: Waldthausen, J... von Recipient: Haeckel, Ernst Corporation: Deutsche Gesandtschaft Dating: 11.03.1907
POSTKARTE Schuster, Adolf Niklaus Author: Schuster, Adolf Niklaus Recipient: Haeckel, Ernst Dating: 11.03.1910
BRIEF [O.A.] Sangmineti, Alfred Geróme Author: Sangmineti, Alfred Geróme Recipient: Haeckel, Ernst Dating: 21.12.1904