BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 10.01.1902
BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 10.05.1902
BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 24.07.1902
BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 24.10.1902