BRIEF [O.A.] Vosberg Author: Vosberg Recipient: Haeckel, Ernst Corporation: Der Magistrat der Residenzstadt Postdam Dating: 29.01.1919
BRIEF [O.A.] Vosberg Author: Vosberg Recipient: Haeckel, Ernst Corporation: Der Oberbürgermeister Dating: 11.01.1919
BRIEF [O.A.] Schlicht, von [?] Author: Schlicht, von [?] Recipient: Haeckel, Ernst Dating: 14.07.1876