BRIEF [O.A.] Dieckmann, Gertha Author: Dieckmann, Gertha Recipient: Haeckel, Walter Dating: 17.01.1923
BRIEF [O.A.] Finsterlin, Hermann Author: Finsterlin, Hermann Recipient: Haeckel, Walter Dating: 13.02.1918
BRIEF [O.A.] Unbekannt Author: Unbekannt Recipient: Haeckel, Walter Corporation: Wilhelm Engelmann Verlagsbuchhandlung Dating: 10.02.1921
BRIEF [O.A.] N.N. Author: N.N. Recipient: Haeckel, Walter Corporation: The Rationalist Press Association Dating: 10.09.1919
BRIEF OHNE UMSCHLAG Rottenburg, Paul Author: Rottenburg, Paul Recipient: Haeckel, Walter Dating: ??.12.1914
BRIEF OHNE UMSCHLAG Rottenburg, Paul Author: Rottenburg, Paul Recipient: Haeckel, Walter Dating: 29.05.1912
