BRIEF [O.A.] Hentschel, Willibald Author: Hentschel, Willibald Recipient: Haeckel, Ernst Dating: 10.12.1906
BRIEF [O.A.] Hentschel, Willibald Author: Hentschel, Willibald Recipient: Haeckel, Ernst Dating: 26.11.1906
BRIEF [O.A.] Hentschel, Willibald Author: Hentschel, Willibald Recipient: Haeckel, Ernst Dating: 05.06.1906