BRIEF OHNE UMSCHLAG Daelen, Eduard Author: Daelen, Eduard Recipient: Haeckel, Ernst Dating: 30.08.1919
BRIEF [O.A.] Flechtheim, Alfred Author: Flechtheim, Alfred Recipient: Haeckel, Ernst Corporation: Galerie Alfred Flechtheim G.m.b.H. Dating: 17.02.1919
BRIEF OHNE UMSCHLAG Monjé, Paula (1849-1919) Author: Monjé, Paula (1849-1919) Recipient: Haeckel, Ernst Dating: 23.01.1919