BRIEF [O.A.] Trautmann, Heinrich Author: Trautmann, Heinrich Recipient: Haeckel, Ernst Dating: 07.08.1903
BRIEF OHNE UMSCHLAG Lampert, Friedrich Ernst Wilhelm Author: Lampert, Friedrich Ernst Wilhelm Recipient: Haeckel, Carl Gottlob Dating: 19.02.1864
TELEGRAMM Engelmann, Theodor Wilhelm Author: Engelmann, Theodor Wilhelm Recipient: Haeckel, Walter Dating: 12.08.1919