BRIEF [O.A.] Recipient: Haeckel, Walter Corporation: The Rationalist Press Association Dating: 10.09.1919
BRIEF OHNE UMSCHLAG Gegenbaur, Fritz Author: Gegenbaur, Fritz Recipient: Haeckel, Walter Dating: 17.12.1912
BRIEF OHNE UMSCHLAG Arrhenius, Svante Author: Arrhenius, Svante Recipient: Haeckel, Walter Dating: 23.05.1920
BRIEF OHNE UMSCHLAG Ade, Mathilde Author: Ade, Mathilde Recipient: Haeckel, Walter Dating: 25.10.1903
BRIEF [O.A.] Krauseneck, Valentine Author: Krauseneck, Valentine Recipient: Haeckel, Walter Dating: 25.07.1927
BRIEF [O.A.] Melliess, W... Author: Melliess, W... Recipient: Haeckel, Walter Corporation: Bibliographisches Institut Dating: 18.02.1921
BRIEF [O.A.] Haeckel, Heinrich Author: Haeckel, Heinrich Recipient: Haeckel, Walter Dating: 10.11.1919