BRIEF [O.A.] Jousset de Bellesme Author: Jousset de Bellesme Recipient: Haeckel, Ernst Dating: 21.01.1910
PORTRÄTPOSTKARTE Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 24.08.1910
BRIEF [O.A.] Penninckx, Henry Author: Penninckx, Henry Recipient: Haeckel, Ernst Corporation: Jeunesse Progressiste Dating: 03.08.1910