POSTKARTE Keidel, Johann E... Author: Keidel, Johann E... Recipient: Haeckel, Ernst Dating: 23.03.1908
POSTKARTE Keidel, Johann E... Author: Keidel, Johann E... Recipient: Haeckel, Ernst Dating: 08.03.1908
BRIEF [O.A.] Keidel, Johann E... Author: Keidel, Johann E... Recipient: Haeckel, Ernst Dating: 07.03.1908