BRIEF OHNE UMSCHLAG Haeckel, Karl Author: Haeckel, Karl Recipient: Sethe, Christoph Dating: 01.06.1836
BRIEF OHNE UMSCHLAG Merkel, Christiane Author: Merkel, Christiane Recipient: Haeckel, Ernst Dating: 04.10.1858
BRIEF OHNE UMSCHLAG Merkel, Christiane Author: Merkel, Christiane Recipient: Haeckel, Ernst Dating: 22.06.1875
