POSTKARTE Sokolowsky, Alexander Author: Sokolowsky, Alexander Recipient: Haeckel, Ernst Dating: 11.12.1906
BRIEF OHNE UMSCHLAG Sokolowsky, Alexander Author: Sokolowsky, Alexander Recipient: Haeckel, Ernst Dating: 29.03.1906
BRIEF OHNE UMSCHLAG Sokolowsky, Alexander Author: Sokolowsky, Alexander Recipient: Haeckel, Ernst Dating: 18.02.1906
BRIEF OHNE UMSCHLAG Sokolowsky, Alexander Author: Sokolowsky, Alexander Recipient: Haeckel, Ernst Dating: 08.03.1906
BRIEF [O.A.] Fürst, Moritz Author: Fürst, Moritz Recipient: Haeckel, Ernst Corporation: Archiv für Soziale Medizin und Hygiene Dating: 03.01.1906