BRIEF OHNE UMSCHLAG Strasburger, Eduard Author: Strasburger, Eduard Recipient: Haeckel, Ernst Dating: 01.09.1882
BRIEF [O.A.] Brunnhofer, Hermann Author: Brunnhofer, Hermann Recipient: Haeckel, Ernst Corporation: Aargauische Kantonsbibliothek Dating: 14.11.1882
BRIEF OHNE UMSCHLAG Keller, Conrad Author: Keller, Conrad Recipient: Haeckel, Ernst Dating: 18.05.1882