BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Carl Gottlob; Haeckel, Charlotte Dating: 23.08.1868
BRIEF OHNE UMSCHLAG Leitem, Rudolph Author: Leitem, Rudolph Recipient: Haeckel, Ernst Dating: 13.02.1909
BRIEF OHNE UMSCHLAG Katzenstein, Herbert Author: Katzenstein, Herbert Recipient: Haeckel, Ernst Dating: 13.02.1904
