BRIEF [O.A.] Knieling, Johs... W... Author: Knieling, Johs... W... Recipient: Haeckel, Ernst Dating: 22.02.1919
BRIEF [O.A.] Jacoby, H... E... L... Author: Jacoby, H... E... L... Recipient: Haeckel, Ernst Dating: 14.02.1919
BRIEF [O.A.] Walther, Johannes Author: Walther, Johannes Recipient: Haeckel, Ernst Dating: 16.02.1919
BRIEF [O.A.] Waldthausen, Ellen Author: Waldthausen, Ellen Recipient: Haeckel, Ernst Dating: 04.02.1919