BRIEF OHNE UMSCHLAG Schleicher, August Author: Schleicher, August Recipient: Haeckel, Ernst Dating: 09.03.1863
BRIEF OHNE UMSCHLAG Schleicher, August Author: Schleicher, August Recipient: Haeckel, Ernst Dating: 05.09.1863
BILLET Schleicher, August Author: Schleicher, August Recipient: Haeckel, Ernst; Haeckel, Anna Dating: 29.10.1863