BRIEF [O.A.] Heyer, Carl August Author: Heyer, Carl August Recipient: Haeckel, Ernst Corporation: Chemisches Untersuchungsamt Dating: 12.11.1917
BRIEF [O.A.] Heyer, Carl August Author: Heyer, Carl August Recipient: Haeckel, Ernst Corporation: Chemisches Untersuchungsamt Dating: 21.11.1917