BRIEF OHNE UMSCHLAG Unna, Paul Gerson Author: Unna, Paul Gerson Recipient: Haeckel, Ernst Dating: 21.11.1917
BRIEF OHNE UMSCHLAG Sokolowsky, Alexander Author: Sokolowsky, Alexander Recipient: Haeckel, Ernst Dating: 07.03.1917
BRIEF OHNE UMSCHLAG Droste, Julius Author: Droste, Julius Recipient: Haeckel, Ernst Dating: 14.08.1917