BRIEF OHNE UMSCHLAG Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 22.04.1863
BRIEF [O.A.] Gierlichs, Florentine Author: Gierlichs, Florentine Recipient: Haeckel, Ernst Dating: 03.12.1863
BRIEF [O.A.] Gessenhardt, Johann Author: Gessenhardt, Johann Recipient: Haeckel, Ernst Dating: 21.05.1863