BRIEF [O.A.] Funder, A... V... M... Author: Funder, A... V... M... Recipient: Haeckel, Ernst Dating: 16.06.1916
BRIEF OHNE UMSCHLAG Fürbringer, Max Author: Fürbringer, Max Recipient: Haeckel, Ernst Dating: ??.02.1916
BRIEF OHNE UMSCHLAG Fürbringer, Max Author: Fürbringer, Max Recipient: Haeckel, Ernst Dating: 18.05.1916