BRIEF [O.A.] Hentschel, Willibald Author: Hentschel, Willibald Recipient: Haeckel, Ernst Dating: 25.01.1891
BRIEF [O.A.] Hentschel, Willibald Author: Hentschel, Willibald Recipient: Haeckel, Ernst Dating: 02.02.1891
BRIEF [O.A.] Hentschel, Willibald Author: Hentschel, Willibald Recipient: Haeckel, Ernst Dating: 10.03.1891