BRIEF [O.A.] Rosenthal, Alfred Author: Rosenthal, Alfred Recipient: Haeckel, Ernst Dating: 10.06.1905
BRIEF [O.A.] Rühm, Julius Author: Rühm, Julius Recipient: Haeckel, Ernst Corporation: Deutscher Monistenbund, Ortsgruppe Nürnberg Dating: 07.03.1908
