BRIEF [O.A.] Hirth, Georg Author: Hirth, Georg Recipient: Haeckel, Ernst Corporation: Jugend Dating: 11.12.1903
BRIEF [O.A.] Hirth, Georg Author: Hirth, Georg Recipient: Haeckel, Ernst Corporation: Jugend Dating: 22.12.1903
BRIEF [O.A.] Hirzel, Georg Author: Hirzel, Georg Recipient: Haeckel, Ernst Corporation: S. Hirzel, Verlagsbuchhandlung Dating: 28.10.1903