BILDPOSTKARTE Altmann-Bronn, Ida Author: Altmann-Bronn, Ida Recipient: Haeckel, Ernst Dating: 26.09.1913
BRIEF OHNE UMSCHLAG Ankenbrand, Ludwig Author: Ankenbrand, Ludwig Recipient: Haeckel, Ernst Corporation: Weltreisegesellschaft Ankenbrand-Beckmann Dating: 18.06.1912
BRIEF OHNE UMSCHLAG Brown, Frederick Author: Brown, Frederick Recipient: Haeckel, Ernst Dating: 20.11.1903
BRIEF OHNE UMSCHLAG Brown, Frederick Author: Brown, Frederick Recipient: Haeckel, Ernst Corporation: Granet Brown & Co. Dating: 17.11.1903