BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 03.07.1899
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
BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: ??.01.1904
BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 23.10.1907
BRIEF [O.A.] Muller, H... C... Author: Muller, H... C... Recipient: Haeckel, Ernst Dating: 18.10.1907