BRIEF [O.A.] Semon, Richard W... Author: Semon, Richard W... Recipient: Haeckel, Elisabeth Dating: 22.04.1915
BRIEF [O.A.] Ritter, Paul von Author: Ritter, Paul von Recipient: Haeckel, Elisabeth Dating: 15.03.1891
BRIEF [O.A.] Hintze, Wilhelmine Author: Hintze, Wilhelmine Recipient: Haeckel, Elisabeth Dating: 02.05.1915