BRIEF [O.A.] Poritzky, J... E... Author: Poritzky, J... E... Recipient: Haeckel, Ernst Dating: 13.05.1901
BRIEF [O.A.] Poritzky, J... E... Author: Poritzky, J... E... Recipient: Haeckel, Ernst Dating: 29.07.1901
BRIEF [O.A.] Poritzky, J... E... Author: Poritzky, J... E... Recipient: Haeckel, Ernst Dating: 19.09.1901
BRIEF [O.A.] Poritzky, J... E... Author: Poritzky, J... E... Recipient: Haeckel, Ernst Dating: 30.09.1901
POSTKARTE Poritzky, J... E... Author: Poritzky, J... E... Recipient: Haeckel, Ernst Dating: 02.10.1901