BRIEF [O.A.] Reich, Otto & Ernst Wolfgang Author: Reich, Otto & Ernst Wolfgang Recipient: Haeckel, Ernst Dating: 15.02.1917
POSTKARTE Reich, Otto & Ernst Wolfgang Author: Reich, Otto & Ernst Wolfgang Recipient: Haeckel, Ernst Dating: 07.03.1917
BRIEF [O.A.] Reich, Ernst Wolfgang Author: Reich, Ernst Wolfgang Recipient: Haeckel, Ernst Dating: 15.02.1918
BRIEF [O.A.] Reich, Ernst Wolfgang Author: Reich, Ernst Wolfgang Recipient: Haeckel, Ernst Dating: 15.02.1919