BRIEF OHNE UMSCHLAG Bernardelli, Paul Author: Bernardelli, Paul Recipient: Haeckel, Ernst Dating: 06.09.1908
POSTKARTE Bentenschneider, Otto Author: Bentenschneider, Otto Recipient: Haeckel, Ernst Dating: 24.03.1908
BRIEF [O.A.] Recipient: Haeckel, Ernst Corporation: Deutscher Monistenbund, Ortsgruppe Magdeburg Dating: 02.03.1908