BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Göppert, Heinrich Robert Dating: 07.07.1874
BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Stremayr, Karl Ritter von Dating: 25.12.1870
BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Stremayr, Karl Ritter von Dating: ca. 25.01.1871