BRIEF [O.A.] Dieckmann, Gertha Author: Dieckmann, Gertha Recipient: Haeckel, Ernst Dating: 08.12.1899
BRIEF [O.A.] Dieckmann, Gertha Author: Dieckmann, Gertha Recipient: Haeckel, Ernst Dating: 25.01.1900
BRIEF [O.A.] Dieckmann, Gertha Author: Dieckmann, Gertha Recipient: Haeckel, Ernst Dating: 11.05.1900
BRIEF [O.A.] Dieckmann, Gertha Author: Dieckmann, Gertha Recipient: Haeckel, Ernst Dating: 06.02.1913
BRIEF [O.A.] Dieckmann, Gertha Author: Dieckmann, Gertha Recipient: Haeckel, Ernst Dating: 17.02.1913
MANUSKRIPT Douwes Dekker, Eduard Author: Douwes Dekker, Eduard Recipient: Haeckel, Ernst Dating: ??.??.1876
BRIEF [O.A.] Frohmu, Friedrich Author: Frohmu, Friedrich Recipient: Haeckel, Ernst Dating: 15.09.1910